9,885

^[1]

7,716

7,978

Diluted Earnings Per Share

$ 25,014

$ 24,348

$ 23,056

Basic Earnings Per Share

$ 2.04

$ 1.99

$ 1.85

$ 2.01

$ 1.96

$ 1.82

[1]	Includes one-time, non-cash TCJA charge of $1,824,000

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Comprehensive income:
Net income	$ 25,014	$ 24,348	$ 23,056
Other comprehensive income:
Net unrealized gain (loss) on securities available-for-sale	6,637	(10,644)	1,527
Tax effect	(2,465)	3,954	(567)
Reclassification adjustments for gains included in net income		(387)	(2,910)
Tax effect		144	1,081
FASB ASC 715 adjustment	(1,311)	(1,435)	6,256
Tax effect	487	531	(2,324)
Foreign currency translation adjustments	161	(42)	(96)
Total comprehensive income	$ 28,523	$ 16,469	$ 26,023

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities:
Net income	$ 25,014	$ 24,348	$ 23,056
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,341	9,429	8,859
Net gains on sales of securities		(387)	(2,910)
Stock-based compensation expense	2,339	1,959	2,059
Provisions for loan losses		(1,500)	(850)
Deferred income tax expense (benefit)	3,997	319	(137)
(Decrease) increase in current income tax liability	(3,026)	357	47
Increase in pension liability	8,008	4,137	4,550
Increase in accounts receivable	(4,656)	(4,070)	(839)
Other operating activities, net	(4,127)	597	(342)
Net cash provided by operating activities	38,890	35,189	33,493
Cash Flows From Investing Activities:
Proceeds from sales of securities available-for-sale		21,491	99,347
Proceeds from maturities of securities available-for-sale	44,156	43,524	38,460
Purchase of securities available-for-sale	(124,777)	(96,290)	(161,279)
Net (increase) decrease in loans	(21,335)	(5,771)	10,882
(Increase) decrease in payments in excess of funding	(33,756)	179	14,701
Purchases of premises and equipment, net	(4,127)	(4,684)	(5,747)
Net cash used in investing activities	(139,839)	(41,551)	(3,636)
Cash Flows From Financing Activities:
Net increase in noninterest-bearing demand deposits	66,885	32,833	22,824
Net (decrease) increase in interest-bearing demand and savings deposits	(7,472)	(51,440)	23,536
Net decrease in time deposits	(3,286)	(5,916)	(18,075)
Net increase (decrease) in accounts and drafts payable	19,601	65,028	(78,169)
Cash dividends paid	(10,675)	(9,979)	(9,697)
Purchase of common shares for treasury	(2,270)	(9,215)	(10,951)
Other financing activities, net	(467)	(1,378)	(488)
Net cash provided by (used in) financing activities	62,316	19,933	(71,020)
Net (decrease) increase in cash and cash equivalents	(38,633)	13,571	(41,163)
Cash and cash equivalents at beginning of year	266,743	253,172	294,335
Cash and cash equivalents at end of year	228,110	266,743	253,172
Supplemental information:
Cash paid for interest	2,178	2,017	2,133
Cash paid for income taxes	$ 7,677	$ 7,061	$ 8,190

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($)
$ in Thousands

Common Stock [Member]

Additional Paid-in Capital [Member]

Retained Earnings [Member]

Treasury Stock [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Total

Balance at Dec. 31, 2014

$ 5,966

$ 126,169

$ 90,635

$ (12,707)

$ (9,631)

$ 200,432

Issuance of common shares pursuant to stock-based compensation plan, net

23,056

Cash dividends

(9,697)

^[1]

(1,250)

797

(453)

Exercise of SARs

(687)

293

(394)

Stock-based compensation expense

2,058

Purchase of common shares

^[1]

(10,591)

Other comprehensive loss

2,967

Balance at Dec. 31, 2015

5,966

126,290

103,994

(22,208)

(6,664)

207,378

Issuance of common shares pursuant to stock-based compensation plan, net

24,348

Cash dividends

(9,979)

^[1]

(1,231)

566

(665)

Exercise of SARs

(1,364)

651

(713)

Stock-based compensation expense

1,959

Purchase of common shares

^[1]

(9,215)

Excess tax benefits associated with stock based compensation

2,801

Other comprehensive loss

(7,879)

Balance at Dec. 31, 2016

5,966

128,455

118,363

(30,206)

(14,543)

208,035

Issuance of common shares pursuant to stock-based compensation plan, net

25,014

Cash dividends

(10,675)

Stock dividend

558

75,108

(75,674)

(8)

^[1]

(821)

273

(548)

Exercise of SARs

(451)

142

(309)

Stock-based compensation expense

2,340

Purchase of common shares

^[1]

(2,270)

Other comprehensive loss

3,509

Other comprehensive income

reclassification for ASU 2018-02

2,286

(2,286)

Balance at Dec. 31, 2017

$ 6,524

$ 204,631

$ 59,314

$ (32,061)

$ (13,320)

$ 225,088

[1]	(1) Share and per share figures adjusted for the 10% stock dividend that occurred on December 15, 2017

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends, per share	$ .87	$ .81	$ 0.77
Stock Issued During Period, Shares, Purchase of Assets	41,846	205,835	238,053
Stock issued pursuant to stock-based compensation	24,482	39,816	47,065

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 1
Summary of Significant Accounting Policies

Summary of Operations Cass Information Systems, Inc. (the “Company”) provides payment and information services, which include processing and payment of transportation, energy, telecommunications and environmental invoices. These services include the acquisition and management of data, information delivery and financial exchange. The consolidated balance sheet captions, “Accounts and drafts payable” and “Payments in excess of funding,” represent the Company’s resulting financial position related to the payment services that are performed for customers. The Company also provides a full range of banking services to individual, corporate and institutional customers through Cass Commercial Bank (the “Bank”), its wholly owned bank subsidiary.

Basis of Presentation The accounting and reporting policies of the Company and its subsidiaries conform to U.S. generally accepted accounting principles (“GAAP”). The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries after elimination of intercompany transactions. Certain amounts in the 2016 and 2015 consolidated financial statements have been reclassified to conform to the 2017 presentation. Such reclassifications have no effect on previously reported net income or shareholders’ equity. The Company issued a 10% stock dividend on December 15, 2017. The share and per share information have been restated unless indicated otherwise for all periods presented in the accompanying consolidated financial statements.

Use of Estimates In preparing the consolidated financial statements, Company management is required to make estimates and assumptions which significantly affect the reported amounts in the consolidated financial statements.

Cash and Cash Equivalents For purposes of the consolidated statements of cash flows, the Company considers cash and due from banks, interest-bearing deposits in other financial institutions, federal funds sold and other short-term investments as segregated in the accompanying consolidated balance sheets to be cash equivalents.

Investment in Debt Securities The Company classifies its debt marketable securities as available-for-sale. Securities classified as available-for-sale are carried at fair value. Unrealized gains and losses, net of the related tax effect, are excluded from earnings and reported in accumulated other comprehensive income, a component of shareholders’ equity. A decline in the fair value of any available-for-sale security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. To determine whether impairment is other than temporary, the Company considers guidance provided in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320 - Investments – Debt and Equity Securities. When determining whether a debt security is other-than-temporarily impaired, the Company assesses whether it has the intent to sell the security and whether it is more likely than not that the Company will be required to sell prior to recovery of the amortized cost basis. Evidence considered in this assessment includes the reasons for impairment, the severity and duration of the impairment, changes in value subsequent to year-end and forecasted performance of the investee. Premiums and discounts are amortized or accreted to interest income over the estimated lives of the securities using the level-yield method. Interest income is recognized when earned. Gains and losses are calculated using the specific identification method.

Allowance for Loan Losses (“ALLL”) The ALLL is increased by provisions charged to expense and is available to absorb charge-offs, net of recoveries. Management utilizes a systematic, documented approach in determining the appropriate level of the ALLL. Management’s approach provides for estimated credit losses on individually evaluated loans in accordance with FASB ASC 310 - Allowance for Credit Losses (“ASC 310”). These estimates are based upon a number of factors, such as payment history, financial condition of the borrower, expected future cash flows and discounted collateral exposure.

Estimated credit losses inherent in the remainder of the portfolio are estimated in accordance with FASB ASC 450 -Contingencies. These loans are segmented into groups based on similar risk characteristics. Historical loss rates for each risk group, which are updated quarterly, are generally quantified using all recorded loan charge-offs and recoveries over a prescribed look-back period. These historical loss rates for each risk group are used as the starting point to determine the level of the allowance. The Company’s methodology incorporates an estimated loss emergence period for each risk group. The loss emergence period is the period of time from when a borrower experiences a loss event and when the actual loss is recognized in the financial statements, generally at the time of initial charge-off of the loan balance. The Company’s methodology also includes qualitative risk factors that allow management to adjust its estimates of losses based on the most recent information available and to address other limitations in the quantitative component that is based on historical loss rates. Such risk factors are generally reviewed and updated quarterly, as appropriate, and are adjusted to reflect changes in national and local economic conditions and developments, the volume and severity of delinquent and internally classified loans, loan concentrations, assessment of trends in collateral values, assessment of changes in borrowers’ financial stability, and changes in lending policies and procedures, including underwriting standards and collections, charge-off and recovery practices.

Management believes the ALLL is adequate to absorb probable losses in the loan portfolio. Additionally, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s ALLL. Such agencies may require the Company to increase the ALLL based on their judgments and interpretations about information available to them at the time of their examinations.

Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed over the estimated useful lives of the assets, or the respective lease terms for leasehold improvements, using straight-line and accelerated methods. Estimated useful lives do not exceed 40 years for buildings, the lesser of 10 years or the life of the lease for leasehold improvements and range from 3 to 7 years for software, equipment, furniture and fixtures. Maintenance and repairs are charged to expense as incurred.

Intangible Assets Cost in excess of fair value of net assets acquired has resulted from business acquisitions. Goodwill and intangible assets with indefinite useful lives are not amortized, but instead are tested for impairment at least annually. Intangible assets with definite useful lives are amortized on a straight-line basis over their respective estimated useful lives.

Periodically, the Company reviews intangible assets for events or changes in circumstances that may indicate that the carrying amount of the assets may not be recoverable. Based on those reviews, adjustments of recorded amounts have not been required.

Non-marketable Equity Investments The Company accounts for non-marketable equity investments, in which it holds less than a 20% ownership, under the cost method. Under the cost method of accounting, investments are carried at cost and are adjusted only for other than temporary declines in fair value, distributions of earnings and additional investments. The Company periodically evaluates whether any declines in fair value of its investments are other than temporary. In performing this evaluation, the Company considers various factors including any decline in market price, where available, the investee's financial condition, results of operations, operating trends and other financial ratios. Non-marketable equity investments are included in other assets on the consolidated balance sheets.

Foreclosed Assets Real estate acquired as a result of foreclosure is initially recorded at fair value less estimated selling costs. Fair value is generally determined through the receipt of appraisals. Any write down to fair value at the time the property is acquired is recorded as a charge-off to the allowance for loan losses. Any decline in the fair value of the property subsequent to acquisition is recorded as a charge to non-interest expense.

Treasury Stock Purchases of the Company’s common stock are recorded at cost. Upon reissuance, treasury stock is reduced based upon the average cost basis of shares held.

Comprehensive Income Comprehensive income consists of net income, changes in net unrealized gains (losses) on available-for-sale securities and pension liability adjustments and is presented in the accompanying consolidated statements of shareholders' equity and consolidated statements of comprehensive income.

Loans Interest on loans is recognized based upon the principal amounts outstanding. It is the Company’s policy to discontinue the accrual of interest when there is reasonable doubt as to the collectability of principal or interest. Subsequent payments received on such loans are applied to principal if there is any doubt as to the collectability of such principal; otherwise, these receipts are recorded as interest income. The accrual of interest on a loan is resumed when the loan is current as to payment of both principal and interest and/or the borrower demonstrates the ability to pay and remain current. Loan origination and commitment fees on originated loans, net of certain direct loan origination costs, are deferred and amortized to interest income using the level-yield method over the estimated lives of the related loans.

Impairment of Loans A loan is considered impaired when it is probable that a creditor will be unable to collect all amounts due, both principal and interest, according to the contractual terms of the loan agreement. When measuring impairment, the expected future cash flows of an impaired loan are discounted at the loan's effective interest rate. Alternatively, impairment could be measured by reference to an observable market price, if one exists, or the fair value of the collateral for a collateral-dependent loan. Regardless of the historical measurement method used, the Company measures impairment based on the fair value of the collateral when the Company determines foreclosure is probable. Additionally, impairment of a restructured loan is measured by discounting the total expected future cash flows at the loan's effective rate of interest as stated in the original loan agreement. The Company uses its nonaccrual methods as discussed above for recognizing interest on impaired loans.

Information Services Revenue A majority of the Company’s revenues are attributable to fees for providing services. These services include transportation invoice rating, payment processing, auditing, and the generation of accounting and transportation information. The Company also processes, pays and generates management information from electric, gas, telecommunications, environmental, and other invoices. The specific payment and information processing services provided to each customer are developed individually to meet each customer’s specific requirements. The Company enters into service agreements with customers typically for fixed fees per transaction that are invoiced monthly. Revenues are recognized in the period services are rendered and earned under the service agreements, as long as collection is reasonably assured.

Income Taxes Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. Deferred tax assets are reduced if necessary, by a deferred tax asset valuation allowance. In the event that management determines it is more likely than not that it will not be able to realize all or part of net deferred tax assets in the future, the Company adjusts the recorded value of deferred tax assets, which would result in a direct charge to income tax expense in the period that such determination is made. Likewise, the Company will reverse the valuation allowance when realization of the deferred tax asset is expected. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.

Earnings Per Share Basic earnings per share is computed by dividing net income by the weighted average number of common shares outstanding. Diluted earnings per share is computed by dividing net income by the sum of the weighted average number of common shares outstanding and the weighted average number of potential common shares outstanding.

Stock-Based Compensation The Company follows FASB ASC 718 - Accounting for Stock Options and Other Stock-based Compensation (“ASC 718”), which requires that all stock-based compensation be recognized as an expense in the financial statements and that such cost be measured at the fair value of the award. FASB ASC 718 also requires that excess tax benefits related to stock option exercises and restricted stock awards be reflected as financing cash inflows instead of operating cash inflows.

Pension Plans The amounts recognized in the consolidated financial statements related to pension are determined from actuarial valuations. Inherent in these valuations are assumptions including expected return on plan assets, discount rates at which the liabilities could be settled at December 31, 2017, rate of increase in future compensation levels and mortality rates. These assumptions are updated annually and are disclosed in Note 10. The Company follows FASB ASC 715 - Compensation – Retirement Benefits (“ASC 715”), which requires companies to recognize the overfunded or underfunded status of a defined benefit postretirement plan as an asset or liability in its consolidated balance sheet and to recognize changes in that funded status in the year in which the changes occur through comprehensive income. The funded status is measured as the difference between the fair value of the plan assets and the projected benefit obligation as of the date of its fiscal year-end.

Fair Value Measurements The Company follows the provisions of FASB ASC 820 - Fair Value Measurements and Disclosures, which defines fair value, establishes a framework for measuring fair value in GAAP, and outlines disclosures about fair value measurements. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. A three-level hierarchy for valuation techniques is used to measure financial assets and financial liabilities at fair value. This hierarchy is based on whether the valuation inputs are observable or unobservable. Financial instrument valuations are considered Level 1 when they are based on quoted prices in active markets for identical assets or liabilities. Level 2 financial instrument valuations use quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Financial instrument valuations are considered Level 3 when they are determined using pricing models, discounted cash flow methodologies or similar techniques and at least one significant model assumption or input is unobservable, and when determination of the fair value requires significant management judgment or estimation. The Company records securities available for sale at their fair values on a recurring basis using Level 2 valuations. Additionally, the Company records impaired loans and other real estate owned at their fair value on a nonrecurring basis. The nonrecurring fair value adjustments typically involve application of lower-of-cost-or-market accounting or impairment write-downs of individual assets.

Impact of New and Not Yet Adopted Accounting Pronouncements

In May 2014, the FASB issued Accounting Standards Update (“ASU”) No. 2014-09 – Revenue from Contracts with Customers. The ASU supersedes revenue recognition requirements in Topic 605, Revenue Recognition, including most industry-specific revenue recognition guidance in the FASB Accounting Standards Codification (“ASC”). The core principle of the new guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance identifies specific steps that entities should apply in order to achieve this principle. Under the ASU, the amendments are effective for interim and annual periods beginning January 1, 2018 and must be applied retrospectively. The Company’s revenue is comprised of net interest income on financial assets and liabilities, which is explicitly excluded from the scope, and non-interest income. The Company will use the modified retrospective transition approach and there will not be a significant impact on the Company’s consolidated financial statements or results of operations.

In January 2016, the FASB issued ASU No. 2016-01 – Financial Instruments – Overall (ASC Subtopic 825-10). The ASU requires an entity to: (i) measure equity investments at fair value through net income, with certain exceptions; (ii) present in OCI the changes in instrument-specific credit risk for financial liabilities measured using the fair value option; (iii) present financial assets and financial liabilities by measurement category and form of financial asset; (iv) calculate the fair value of financial instruments for disclosure purposes based on an exit price and; (v) assess a valuation allowance on deferred tax assets related to unrealized losses of AFS debt securities in combination with other deferred tax assets. The standard is effective for fiscal periods beginning January 1, 2018 and will not have a significant impact on the Company’s consolidated financial statements or results of operations.

In February 2016, the FASB issued ASU No. 2016-02 – Leases (ASC Topic 842). The ASU improves financial reporting about leasing transactions. The ASU affects all companies and other organizations that lease assets such as real estate, airplanes, and manufacturing equipment. Consistent with current generally accepted accounting principles (GAAP), the recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily will depend on its classification as a finance or operating lease. However, unlike current GAAP—which requires only capital leases to be recognized on the balance sheet—the new ASU will require both types of leases to be recognized on the balance sheet. The ASU also will require disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. These disclosures include qualitative and quantitative requirements, providing additional information about the amounts recorded in the financial statements. The ASU on leases will take effect for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. A third-party vendor solution has been selected to assist in the application of ASU 2016-02. The impact of the adoption of this ASU is currently being evaluated but is not expected to have a material impact on the Company’s consolidated financial statements or results of operations.

In June 2016, the FASB issued ASU No. 2016-13 - Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The ASU requires measurement and recognition of expected credit losses for financial assets held. Under this standard, it will be required to hold an allowance equal to the expected life-of-loan losses on the loan portfolio. The standard is effective for fiscal periods beginning after December 15, 2019. The impact of the adoption of this ASU is currently being evaluated.

In February 2018, the FASB issued ASU No. 2018-02 – Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The ASU provides for the reclassification of the effect of remeasuring deferred tax balances related to items within AOCI to retained earnings resulting from the TCJA. The Company early adopted, and as a result, reclassified $2,286,000 from AOCI to retained earnings.

Capital Requirements and Regulatory Restrictions

12 Months Ended

Dec. 31, 2017

Regulatory Capital Requirements [Abstract]

Capital Requirements and Regulatory Restrictions

Note 2
Capital Requirements and Regulatory Restrictions

The Company and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can result in certain mandatory, and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s consolidated financial statements. Under capital adequacy guidelines, the Company and the Bank must meet specific capital guidelines that involve quantitative measures of assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The Company’s and the Bank’s capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings and other factors.

Quantitative measures established by regulators to ensure capital adequacy require the Company and the Bank to maintain minimum amounts and ratios of total and Tier I capital and common equity Tier I capital to risk-weighted assets, and of Tier I capital to average assets. Management believes that as of December 31, 2017 and 2016, the Company and the Bank met all capital adequacy requirements to which they are subject.

Effective July 2, 2013, the Federal Reserve Board approved final rules known as the “Basel III Capital Rules” that substantially revised the risk-based capital and leverage capital requirements applicable to bank holding companies and depository institutions, including the Company and the Bank. The Basel III Capital Rules implement aspects of the Basel III capital framework agreed upon by the Basel Committee and incorporate changes required by the Dodd-Frank Wall Street Reform and Consumer Protection Act. Among other things, the Basel III Capital Rules establish stricter capital requirements and calculation standards, as well as more restrictive risk weightings for certain loans and facilities. The Basel III Capital Rules were effective for the Company and the Bank on January 1, 2015 (subject to a phase-in period).

The Bank is also subject to the regulatory framework for prompt corrective action. As of December 31, 2017, the most recent notification from the regulatory agencies categorized the Bank as well-capitalized. To be categorized as well-capitalized, the Bank must maintain minimum total risk-based, common equity Tier I risk-based, Tier I risk-based, and Tier I leverage ratios as set forth in the table below. There are no conditions or events since that notification that management believes have changed the Bank’s category.

Subsidiary dividends can be a significant source of funds for payment of dividends by the Company to its shareholders. At December 31, 2017, unappropriated retained earnings of $30,137,000 were available at the Bank for the declaration of dividends to the Company without prior approval from regulatory authorities. However, dividends paid by the Bank to the Company would be prohibited if the effect thereof would cause the Bank’s capital to be reduced below applicable minimum capital requirements.

There were no restricted funds on deposit used to meet regulatory reserve requirements at December 31, 2017 and 2016.

The Company’s and the Bank’s actual and required capital amounts and ratios are as follows:

					Capital				Requirement to be
	Actual				Requirements				Well-Capitalized
(In thousands)	Amount		Ratio		Amount		Ratio		Amount		Ratio
At December 31, 2017
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	234,389	22.53	%	$	83,233	8.00	%	$	N/A	N/A	%
Cass Commercial Bank		122,440	17.01			57,568	8.00			71,960	10.00
Common Equity Tier I Capital (to risk-weighted assets)
Cass Information Systems, Inc.		224,184	21.55			46,819	4.50			N/A	N/A
Cass Commercial Bank		114,603	15.93			32,382	4.50			46,774	6.50
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		224,184	21.55			62,425	6.00			N/A	N/A
Cass Commercial Bank		114,603	15.93			43,176	6.00			57,568	8.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		224,184	13.87			64,649	4.00			N/A	N/A
Cass Commercial Bank		114,603	14.99			30,581	4.00			38,227	5.00
At December 31, 2016
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	219,747	22.75	%	$	77,272	8.00	%	$	N/A	N/A	%
Cass Commercial Bank		110,576	16.72			52,898	8.00			66,123	10.00
Common Equity Tier I Capital (to risk-weighted assets)
Cass Information Systems, Inc.		209,572	21.70			43,466	4.50			N/A	N/A
Cass Commercial Bank		102,769	15.54			29,755	4.50			42,980	6.50
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		209,572	21.70			57,954	6.00			N/A	N/A
Cass Commercial Bank		102,769	15.54			39,674	6.00			52,898	8.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		209,572	13.83			60,620	4.00			N/A	N/A
Cass Commercial Bank		102,769	13.98			29,409	4.00			36,761	5.00

Investments, Debt and Equity Securities [Abstract]

The entire disclosure for banks, savings institutions, and credit unions, for regulatory capital requirements imposed by the Federal Reserve System (FRB), the Federal Deposit Insurance Corporation (FDIC), the Office of Thrift Supervision (OTS) or for any state imposed capital requirements, as applicable. The disclosure may include (1) a description of regulatory capital requirements (a) for capital adequacy purposes and (b) established by the prompt corrective action provisions of Section 38 of the Federal Depository Insurance Act; (2) the actual or possible material effects of noncompliance with such requirements; (3) whether the entity is in compliance with the regulatory capital requirements including (a) required and actual ratios and amounts of Tier 1 leverage, Tier 1 risk-based, and total risk-based capital, tangible capital (for savings institutions), and Tier 3 capital for market risk (for certain banks and bank holding companies), (b) factors that may significantly affect capital adequacy; (4) the prompt corrective action category in which the entity was classified as of its most recent notification; (5) whether management believes any conditions or events since notification have changed the entity's category. Also may include additional information that might be disclosed in situations where substantial doubt about the entity's ability to continue as a going concern for a reasonable period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1G
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958577-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1C
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958572-112826

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1E
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958574-112826

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958569-112826

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1F
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958575-112826

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1D
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958573-112826

+ Details

Investment in Securities

12 Months Ended

Dec. 31, 2017

Investment in Securities

Note 3
Investment in Securities

Investment securities available-for-sale are recorded at fair value on a recurring basis. The Company’s investment securities available-for-sale at December 31, 2017 and 2016 are measured at fair value using Level 2 valuations. The market evaluation utilizes several sources which include “observable inputs” rather than “significant unobservable inputs” and therefore falls into the Level 2 category. The table below presents the balances of securities available-for-sale measured at fair value on a recurring basis. The amortized cost, gross unrealized gains, gross unrealized losses and fair value of debt and equity securities are summarized as follows:

	December 31, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized
(In thousands)	Cost		Gains		Losses		Fair Value
State and political subdivisions	$	408,165	$	9,528	$	661	$	417,032
U.S. government agencies		46,222		—		722		45,500
Certificates of deposit		7,991		—		—		7,991
Total	$	462,378	$	9,528	$	1,383	$	470,523

	December 31, 2016
			Gross		Gross
	Amortized		Unrealized		Unrealized
(In thousands)	Cost		Gains		Losses		Fair Value
State and political subdivisions	$	368,223	$	5,239	$	3,328	$	370,134
U.S. government agencies		13,075		—		403		12,672
Certificates of deposit		7,746		—		—		7,746
Total	$	389,044	$	5,239	$	3,731	$	390,552

The fair values of securities with unrealized losses are as follows:


					December 31, 2017
	Less than 12 months				12 months or more				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
(In thousands)	Fair Value		Losses		Fair Value		Losses		Fair value		Losses
State and political subdivisions	$	34,755	$	123	$	31,251	$	538	$	66,006	$	661
U.S. government agencies		34,183		376		11,317		346		45,500		722
Certificates of deposit		—		—		—		—		—		—
Total	$	68,938	$	499	$	42,568	$	884	$	111,506	$	1,383

					December 31, 2016
	Less than 12 months				12 months or more				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
(In thousands)	Fair Value		Losses		Fair Value		Losses		Fair value		Losses
State and political subdivisions	$	140,384	$	3,328	$	—	$	—	$	140,384	$	3,328
U.S. government agencies		12,672		403		—		—		12,672		403
Certificates of deposit		—		—		—		—		—		—
Total	$	153,056	$	3,731	$	—	$	—	$	153,056	$	3,731

There were 64 securities, or 17% of the total (24 greater than 12 months), in an unrealized loss position as of December 31, 2017 compared to 108 securities (none greater than 12 months) in an unrealized loss position as of December 31, 2016. All unrealized losses are reviewed to determine whether the losses are other than temporary. Management believes that all unrealized losses are temporary since they are market driven, the Company does not have the intent to sell the security, and it is more likely than not that the Company will not be required to sell prior to recovery of the amortized basis.

The amortized cost and fair value of debt and equity securities by contractual maturity are shown in the following table. Expected maturities may differ from contractual maturities because borrowers have the right to prepay obligations with or without prepayment penalties.

	December 31, 2017
(In thousands)	Amortized Cost		Fair Value
Due in 1 year or less	$	22,492	$	22,638
Due after 1 year through 5 years		57,922		58,425
Due after 5 years through 10 years		256,396		263,961
Due after 10 years		125,568		125,499
No stated maturity		—		—
Total	$	462,378	$	470,523

The premium related to the purchase of state and political subdivisions was $7,147,000 and $5,749,000 in 2017 and 2016, respectively.

The amortized cost of debt securities pledged to secure public deposits, securities sold under agreements to repurchase and for other purposes at December 31, 2017 and 2016 was $3,750,000.

Proceeds from sales of debt securities classified as available-for-sale were $0 in 2017, $21,491,000 in 2016, and $99,347,000 in 2015. Gross realized gains on the sales in 2017, 2016 and 2015 were $0, $387,000, and $2,910,000, respectively. There were no gross realized losses on sales in 2017, 2016 or 2015.

Loans

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Loans

Note 4
Loans

The Company originates commercial, industrial and real estate loans to businesses and faith-based ministries throughout the metropolitan St. Louis, Missouri area, Orange County, California and other selected cities in the United States. The Company does not have any particular concentration of credit in any one economic sector; however, a substantial portion of the commercial and industrial loans is extended to privately-held commercial companies and franchises in these market areas, and are generally secured by the assets of the business. The Company also has a substantial portion of real estate loans secured by mortgages that are extended to faith-based ministries in its market area and selected cities in the United States.

A summary of loan categories is as follows:

	December 31,
(In thousands)	2017		2016
Commercial and industrial	$	236,394	$	214,767
Real estate
Commercial:
Mortgage		94,675		104,779
Construction		9,359		6,325
Church, church-related:
Mortgage		316,073		321,168
Construction		25,948		11,152
Industrial Revenue Bonds		3,374		6,639
Other		408		36
Total loans	$	686,231	$	664,866

The following table presents the aging of loans by loan categories at December 31, 2017:

	Performing						Nonperforming
							90 Days
			30-59		60-89		and		Non-		Total
(In thousands)	Current		Days		Days		Over		accrual		Loans
Commercial and industrial	$	236,394	$	—	$	—	$	—	$	—	$	236,394
Real estate
Commercial:
Mortgage		94,675		—		—		—		—		94,675
Construction		9,359		—		—		—		—		9,359
Church, church-related:
Mortgage		316,073		—		—		—		—		316,073
Construction		25,948		—		—		—		—		25,948
Industrial Revenue Bonds		3,374		—		—		—		—		3,374
Other		408		—		—		—		—		408
Total	$	686,231	$	—	$	—	$	—	$	—	$	686,231

The following table presents the aging of loans by loan categories at December 31, 2016:

	Performing						Nonperforming
							90 Days
			30-59		60-89		and		Non-		Total
(In thousands)	Current		Days		Days		Over		accrual		Loans
Commercial and industrial	$	214,767	$	—	$	—	$	—	$	—	$	214,767
Real estate
Commercial:
Mortgage		104,534		—		—		—		245		104,779
Construction		6,325		—		—		—		—		6,325
Church, church-related:
Mortgage		321,168		—		—		—		—		321,168
Construction		11,152		—		—		—		—		11,152
Industrial Revenue Bonds		6,639		—		—		—		—		6,639
Other		24		12		—		—		—		36
Total	$	664,609	$	12	$	—	$	—	$	245	$	664,866

The following table presents the credit exposure of the loan portfolio by internally assigned credit grade as of December 31, 2017:

	Loans		Performing		Nonperforming
	Subject to		Loans Subject to		Loans Subject
	Normal		Special		to Special
(In thousands)	Monitoring⁽¹⁾		Monitoring⁽²⁾		Monitoring⁽²⁾		Total Loans
Commercial and industrial	$	234,271	$	2,123	$	—	$	236,394
Real estate
Commercial:
Mortgage		93,788		887		—		94,675
Construction		9,359		—		—		9,359
Church, church-related:
Mortgage		316,042		31		—		316,073
Construction		25,948		—		—		25,948
Industrial Revenue Bonds		3,374		—		—		3,374
Other		408		—		—		408
Total	$	683,190	$	3,041	$	—	$	686,231

^⁽¹⁾	Loans subject to normal monitoring involve borrowers of acceptable-to-strong credit quality and risk, who have the apparent ability to satisfy their loan obligation.
^{^{^⁽²⁾}}	Loans subject to special monitoring possess some credit deficiency or potential weakness which requires a high level of management attention.

The following table presents the credit exposure of the loan portfolio by internally assigned credit grade as of December 31, 2016:

	Loans		Performing		Nonperforming
	Subject to		Loans Subject to		Loans Subject to
	Normal		Special		Special
(In thousands)	Monitoring⁽¹⁾		Monitoring⁽²⁾		Monitoring⁽²⁾		Total Loans
Commercial and industrial	$	213,024	$	1,743	$	—	$	214,767
Real estate
Commercial:
Mortgage		103,778		756		245		104,779
Construction		6,325		—		—		6,325
Church, church-related:
Mortgage		318,030		3,138		—		321,168
Construction		11,152		—		—		11,152
Industrial Revenue Bonds		6,639		—		—		6,639
Other		36		—		—		36
Total	$	658,984	$	5,637	$	245	$	664,866

⁽¹⁾	Loans subject to normal monitoring involve borrowers of acceptable-to-strong credit quality and risk, who have the apparent ability to satisfy their loan obligation.
⁽²⁾	Loans subject to special monitoring possess some credit deficiency or potential weakness which requires a high level of management attention.

Impaired loans consist primarily of nonaccrual loans, loans greater than 90 days past due and still accruing interest and troubled debt restructurings, both performing and non-performing. Troubled debt restructuring involves the granting of a concession to a borrower experiencing financial difficulty resulting in the modification of terms of the loan, such as changes in payment schedule or interest rate. There was no ALLL related to impaired loans at both December 31, 2017 and 2016. Nonaccrual loans were $0 and $245,000 at December 31, 2017 and 2016, respectively. There were no loans delinquent 90 days or more and still accruing interest at both December 31, 2017 and 2016. At December 31, 2017 and 2016, there were no loans classified as troubled debt restructuring. The average balances of impaired loans during 2017, 2016 and 2015 were $166,000, $333,000, and $3,188,000, respectively. Income that would have been recognized on non-accrual loans under the original terms of the contract was $24,000, $66,000 and $390,000 for 2017, 2016 and 2015, respectively. Income that was recognized on nonaccrual loans was $17,000, $47,000 and $34,000 for 2017, 2016 and 2015 respectively. There were no foreclosed assets as of December 31, 2017 or December 31, 2016.

There was no recorded investment or unpaid principal balance for impaired loans at December 31, 2017.

The following table presents the recorded investment and unpaid principal balance for impaired loans at December 31, 2016:


					Related
			Unpaid		Allowance
	Recorded		Principal		for Loan
(In thousands)	Investment		Balance		Losses
Commercial and industrial:
Nonaccrual	$	—	$	—	$	—
Real estate
Commercial – Mortgage:
Nonaccrual		245		245		—
Church – Mortgage:
Nonaccrual		—		—		—
Total impaired loans	$	245	$	245	$	—

The Company does not record loans at fair value on a recurring basis. Once a loan is identified as impaired, management measures impairment in accordance with FASB ASC 310. At December 31, 2017, there were no impaired loans. At December 31, 2016, all impaired loans were evaluated based on the fair value of the collateral. The fair value of the collateral is based upon an observable market price or current appraised value and therefore, the Company classifies these assets as nonrecurring Level 3.

A summary of the activity in the allowance for loan losses is as follows:

	December 31,		Charge-							December 31,
(In thousands)	2016		Offs		Recoveries		Provision			2017
Commercial and industrial	$	3,261	$	—	$	30	$	361		$	3,652
Real estate
Commercial:
Mortgage		1,662		—		—		(268	)		1,394
Construction		47		—		—		23			70
Church, church-related:
Mortgage		4,027		—		—		(65	)		3,962
Construction		85		—		—		111			196
Industrial Revenue Bond		101		—		—		(49	)		52
Other		992		—		—		(113	)		879
Total	$	10,175	$	—	$	30	$	—		$	10,205

As of December 31, 2017, there were no loans to affiliates of executive officers or directors.

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

Property, Plant and Equipment [Abstract]

Premises and Equipment

12 Months Ended

Dec. 31, 2017

Premises and Equipment

Note 5
Premises and Equipment

A summary of premises and equipment is as follows:

	December 31,
(In thousands)	2017		2016
Land	$	873	$	873
Buildings		13,386		13,087
Leasehold improvements		2,120		2,098
Furniture, fixtures and equipment		14,801		13,248
Purchased software		4,819		4,704
Internally developed software		16,485		14,377
		52,484		48,387
Less accumulated depreciation		30,898		27,301
Total	$	21,586	$	21,086

Total depreciation charged to expense in 2017, 2016 and 2015 amounted to $3,627,000, $3,245,000 and $3,008,000, respectively.

The Company and its subsidiaries lease various premises and equipment under operating lease agreements which expire at various dates through 2023. Rental expense for 2017, 2016 and 2015 was $1,499,000, $1,397,000 and $1,387,000, respectively. The following is a schedule, by year, of future minimum rental payments required under operating leases that have initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2017:

(In thousands)	Amount
2018	$	1,518
2019		1,270
2020		1,245
2021		1,118
2022		1,086
2023		226
Total	$	6,463

Acquired Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Acquired Intangible Assets

Note 6
Acquired Intangible Assets

The Company accounts for intangible assets in accordance with FASB ASC 350 - Goodwill and Other Intangible Assets (“ASC 350”), which requires that intangibles with indefinite useful lives be tested annually for impairment and those with finite useful lives be amortized over their useful lives.

In March 2017, the Company completed an acquisition and recorded intangible assets of $1,405,000. Those intangibles were valued as $979,000 for goodwill, $355,000 for the customer list and $71,000 for non-compete agreements.

Details of the Company’s intangible assets are as follows:

	December 31, 2017					December 31, 2016
	Gross Carrying		Accumulated			Gross Carrying		Accumulated
(In thousands)	Amount		Amortization			Amount		Amortization
Assets eligible for amortization:
Customer lists	$	4,288	$	(2,702	)	$	3,933	$	(2,342	)
Patent		72		(12	)		72		(8	)
Non-compete agreements		332		(291	)		261		(261	)
Software		234		(234	)		234		(234	)
Other		500		(191	)		500		(158	)
Unamortized intangible assets:
Goodwill⁽¹⁾		12,796		(227	)		11,817		(227	)
Total intangible assets	$	18,222	$	(3,657	)	$	16,817	$	(3,230	)

⁽¹⁾

Amortization through December 31, 2001 prior to adoption of FASB ASC 350.

The customer lists are amortized over seven and ten years; the patents over 18 years, the non-compete agreements over two and five years, software over three years and other intangible assets over 15 years. Amortization of intangible assets amounted to $427,000, $408,000 and $408,000 for the years ended December 31, 2017, 2016 and 2015, respectively. Estimated future amortization of intangibles is $442,000 in 2018, $412,000 2019, $406,000 in both 2020 and 2021 and $88,000 in 2022.

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

Interest-Bearing Deposits [Abstract]

Interest-Bearing Deposits

12 Months Ended

Dec. 31, 2017

Interest-Bearing Deposits

Note 7
Interest-Bearing Deposits

Interest-bearing deposits consist of the following:

	December 31,
(In thousands)	2017			2016
Interest-bearing demand deposits	$	332,881		$	322,091
Savings deposits		11,168			29,430
Time deposits:
Less than $100		2,658			3,523
$100 to less than $250		33,385			37,179
$250 or more		16,455			15,082
Total	$	396,547		$	407,305
Weighted average interest rate		.56	%		.48	%

Interest on deposits consists of the following:

	December 31,
(In thousands)	2017		2016		2015
Interest-bearing demand deposits	$	1,611	$	1,387	$	1,392
Savings deposits		79		100		65
Time deposits:
Less than $100		234		274		346
$100 to less than $250		114		191		119
$250 or more		149		77		189
Total	$	2,187	$	2,029	$	2,111

The scheduled maturities of time deposits are summarized as follows:

	December 31,
	2017				2016
			Percent				Percent
(In thousands)	Amount		of Total		Amount		of Total
Due within:
One year	$	48,370	92.1	%	$	48,740	87.4	%
Two years		281	0.5			4,752	8.5
Three years		2,383	4.5			155	0.3
Four years		25	0.1			2,072	3.7
Five years		1,439	2.8			65	0.1
Total	$	52,498	100.0	%	$	55,784	100.0	%

Unused Available Lines of Credit

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Unused Available Lines of Credit

Note 8
Unused Available Lines of Credit

As of December 31, 2017, the Bank had unsecured lines of credit at correspondent banks to purchase federal funds up to a maximum of $68,000,000 at the following banks: US Bank, $20,000,000; Wells Fargo Bank, $15,000,000; PNC Bank, $12,000,000; Frost National Bank, $10,000,000; JPM Chase Bank, $6,000,000; and UMB Bank $5,000,000. As of December 31, 2017, the Bank had secured lines of credit with the Federal Home Loan Bank (“FHLB”) of $204,789,000 collateralized by commercial mortgage loans. At December 31, 2017, the Company had a line of credit from UMB Bank of $50,000,000 and First Tennessee Bank of $50,000,000 collateralized by state and political subdivision securities. There were no amounts outstanding under any of the lines of credit discussed above at December 31, 2017 or 2016.

Common Stock and Earnings per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Common Stock and Earnings per Share

Note 9
Common Stock and Earnings per Share

The table below shows activity in the outstanding shares of the Company’s common stock during 2017.

	2017
Shares outstanding at January 1	11,188,466
10% stock dividend issued December 15, 2017	1,116,711
Issuance of common stock:
Employee restricted stock grants	3,825
Employee SARs exercised	7,547
Directors’ compensation	8,389
Shares repurchased	(38,042	)
Shares outstanding at December 31	12,286,896

Basic earnings per share is computed by dividing net income by the weighted average number of common shares outstanding. Diluted earnings per share is computed by dividing net income by the sum of the weighted average number of common shares outstanding and the weighted average number of potential common shares outstanding. Under the treasury stock method, stock appreciation rights (“SARs”) are dilutive when the average market price of the Company’s common stock, combined with the effect of any unamortized compensation expense, exceeds the SAR price during a period. Anti-dilutive shares are those SARs with prices in excess of the current market value.

The calculations of basic and diluted earnings per share are as follows:

	December 31,
(In thousands except share and per share data)	2017		2016		2015
Basic:
Net income	$	25,014	$	24,348	$	23,056
Weighted average common shares outstanding		12,250,465		12,265,434		12,494,466
Basic earnings per share	$	2.04	$	1.99	$	1.85
Diluted:
Net income	$	25,014	$	24,348	$	23,056
Weighted average common shares outstanding		12,250,465		12,265,434		12,494,466
Effect of dilutive restricted stock, PBRS and SARs		179,445		172,386		175,784
Weighted average common shares outstanding assuming dilution		12,429,910		12,437,820		12,670,250
Diluted earnings per share	$	2.01	$	1.96	$	1.82

All share and per share data have been restated to give effect to the 10% stock dividend issued on December 15, 2017.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2017

Retirement Benefits [Abstract]

Employee Benefit Plans

Note 10
Employee Benefit Plans

Defined Benefit Plan
The Company has a noncontributory defined-benefit pension plan (the “Plan”), which covers most of its employees. Effective December 31, 2016, the Plan was closed to all new participants. The Company accrues and makes contributions designed to fund normal service costs on a current basis using the projected unit credit with service proration method to amortize prior service costs arising from improvements in pension benefits and qualifying service prior to the establishment of the Plan over a period of approximately 30 years.

A summary of the activity in the Plan’s projected benefit obligation, assets, funded status and amounts recognized in the Company’s consolidated balance sheets is as follows:

(In thousands)	2017			2016
Projected benefit obligation:
Balance, January 1	$	85,551		$	78,369
Service cost		3,733			3,559
Interest cost		3,621			3,505
Actuarial (gain) loss		7,916			2,003
Benefits paid		(2,031	)		(1,885	)
Balance, December 31	$	98,790		$	85,551
Plan assets:
Fair value, January 1	$	73,168		$	71,174
Actual return		10,290			3,879
Employer contribution		—			—
Benefits paid		(2,031	)		(1,885	)
Fair value, December 31	$	81,427		$	73,168
Funded status:
Accrued pension liability	$	(17,363	)	$	(12,383	)

The following represent the major assumptions used to determine the projected benefit obligation of the Plan. For 2017, 2016 and 2015, the Plan’s expected benefit cash flows were discounted using the Citibank Above Median Curve. For 2017, the RP-2014 Mortality Table and the MP-2017 Mortality Improvement Table were used. For 2016, the RP-2014 Mortality Table and MP-2016 Mortality Improvement Table were used. For 2015, the RP-2014 Mortality Table and MP-2015 Mortality Improvement Table were used.

	2017		2016		2015
Weighted average discount rate	3.75	%	4.25	%	4.50	%
Rate of increase in compensation levels	(a)		(a)		(a)

(a)	6.0% graded down to 3.25% over the first seven years of service

The accumulated benefit obligation was $85,236,000 and $74,425,000 as of December 31, 2017 and 2016, respectively. The Company does not expect to make a contribution to the Plan in 2018. The following pension benefit payments, which reflect expected future service, as appropriate, are expected to be paid by the Plan:

	Amount
2018	$	2,679,000
2019		2,823,000
2020		3,045,000
2021		3,300,000
2022		3,693,000
2023-2027		23,682,000

The Plan’s pension cost included the following components:

	For the Year Ended
	December 31,
(In thousands)	2017			2016			2015
Service cost – benefits earned during the year	$	3,733		$	3,559		$	3,796
Interest cost on projected benefit obligations		3,621			3,505			3,178
Expected return on plan assets		(4,681	)		(4,734	)		(4,864	)
Net amortization and deferral		1,382			1,259			1,542
Net periodic pension cost	$	4,055		$	3,589		$	3,652

The following represent the major assumptions used to determine the net pension cost of the Plan:

	2017		2016		2015
Weighted average discount rate	4.25	%	4.50	%	4.00	%
Rate of increase in compensation levels	(a)		(a)		(a)
Expected long-term rate of return on assets	6.50	%	6.75	%	6.75	%

(a)	6.0% graded down to 3.25% over the first seven years of service

For 2017, the RP-2014 Mortality Table and the MP-2016 Mortality Improvement Table were used. For 2016, the RP-2014 Mortality Table and the MP-2015 Mortality Improvement Table were used. For 2015, the RP-2014 Mortality Tables and the MP-2014 Mortality Improvement scale were used.

The investment objective for the Plan is to maximize total return with a tolerance for average risk. Asset allocation is a balance between fixed income and equity investments, with a target allocation of approximately 45% fixed income, 25% U.S. equity and 30% non-U.S. equity. Due to volatility in the market, this target allocation is not always desirable and asset allocations can fluctuate between acceptable ranges. The fixed income component is invested in pooled investment grade securities. The equity components are invested in pooled large cap, small/mid cap and non-U.S. stocks. The expected one-year nominal returns and annual standard deviations are shown by asset class below:

			One-Year Nominal		Annual Standard
Asset Class	% of Total Portfolio		Return		Deviation
Core Fixed Income	51	%	4.55	%	4.55	%
Large Cap U.S. Equities	14	%	7.00	%	15.85	%
Small Cap U.S. Equities	5	%	8.10	%	19.70	%
International (Developed)	25	%	7.99	%	17.93	%
International (Emerging)	5	%	10.56	%	27.35	%

Applying appropriate correlation factors between each of the asset classes the long-term rate of return on assets is estimated to be 6.50%.

A summary of the fair value measurements by type of asset is as follows:

	Fair Value Measurements as of December 31,
	2017						2016
			Quoted Prices						Quoted Prices
			in Active						in Active
			Markets for		Significant				Markets for		Significant
			Identical		Observable				Identical		Observable
			Assets		Inputs				Assets		Inputs
(In thousands)	Total		(Level 1)		(Level 2)		Total		(Level 1)		(Level 2)
Cash	$	374	$	374	$	—	$	340	$	340	$	—
Equity securities
U.S. Large Cap Growth		—		—		—		13,306		—		13,306
U.S. Small/Mid Cap Growth		4,111		—		4,111		5,655		—		5,655
Non-U. S. Core		21,065		—		21,065		10,588		—		10,588
U.S. Large Cap Passive		11,717		—		11,717		7,364		—		7,364
Emerging Markets		4,052		—		4,052		652		—		652
Fixed Income
U.S. Core		11,284		—		11,284		24,438		—		24,438
U.S. Passive		24,345		—		24,345		9,571		—		9,571
Opportunistic		4,479				4,479		1,254				1,254
Total	$	81,427	$	374	$	81,053	$	73,168	$	340	$	72,828

Supplemental Executive Retirement Plan
The Company also has an unfunded supplemental executive retirement plan (“SERP”) which covers key executives of the Company whose benefits are limited by the Internal Revenue Service under the Company’s qualified retirement plan. The SERP is a noncontributory plan in which the Company’s subsidiaries make accruals designed to fund normal service costs on a current basis using the same method and criteria as the Plan.

A summary of the activity in the SERP’s projected benefit obligation, funded status and amounts recognized in the Company’s consolidated balance sheets is as follows:

	December 31,
(In thousands)	2017			2016
Benefit obligation:
Balance, January 1	$	9,132		$	8,748
Service cost		143			133
Interest cost		360			367
Benefits paid		(247	)		(247	)
Actuarial (gain) loss		706			131
Balance, December 31	$	10,094		$	9,132

The following represent the major assumptions used to determine the projected benefit obligation of the SERP. For 2017, 2016 and 2015, the SERP’s expected benefit cash flows were discounted using the Citigroup Above Median Curve.

	2017		2016		2015
Weighted average discount rate	3.50	%	4.00	%	4.25	%
Rate of increase in compensation levels	(a)		(a)		(a)

(a)	6.00% graded down to 3.25% over the first seven years of service.

The accumulated benefit obligation was $8,734,000 and $7,904,000 as of December 31, 2017 and 2016, respectively. Since this is an unfunded plan, there are no plan assets. Benefits paid were $247,000 in both 2017 and 2016 and $243,000 in 2015.

Expected future benefits payable by the Company over the next ten years are as follows:

	Amount
2018	$	314,000
2019		313,000
2020		311,000
2021		367,000
2022		711,000
2023-2027		3,813,000

The SERP’s pension cost included the following components:

	For the Year Ended December 31,
(In thousands)	2017		2016		2015
Service cost – benefits earned during the year	$	143	$	133	$	140
Interest cost on projected benefit obligations		360		367		348
Net amortization and deferral		324		295		654
Net periodic pension cost	$	827	$	795	$	1,142

The pretax amounts in accumulated other comprehensive loss as of December 31 were as follows:

	The Plan				SERP
(In thousands)	2017		2016		2017		2016
Prior service cost	$	—	$	—	$	—	$	—
Net actuarial loss		23,160		22,237		2,388		2,005
Total	$	23,160	$	22,237	$	2,388	$	2,005

The estimated pretax prior service cost and net actuarial loss in accumulated other comprehensive loss at December 31, 2017 expected to be recognized as components of net periodic benefit cost in 2018 for the Plan are $0 and $1,409,000, respectively. The estimated pretax prior service cost and net actuarial loss in accumulated other comprehensive loss at December 31, 2017 expected to be recognized as components of net periodic benefit cost in 2018 for the SERP are $0 and $582,000, respectively.

The Company also maintains a noncontributory profit sharing program, which covers most of its employees. Employer contributions are calculated based upon formulas which relate to current operating results and other factors. Profit sharing expense recognized in the consolidated statements of income in 2017, 2016 and 2015 was $5,799,000, $5,367,000, and $5,211,000, respectively.

The Company also sponsors a defined contribution 401(k) plan to provide additional retirement benefits to substantially all employees. Contributions under the 401(k) plan for 2017, 2016 and 2015 were $925,000, $658,000, and $623,000, respectively.

Stock-based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based Compensation

Note 11
Stock-based Compensation

The Amended and Restated Omnibus Stock and Performance Compensation Plan (the “Omnibus Plan”) provides incentive opportunities for key employees and non-employee directors and to align the personal financial interests of such individuals with those of the Company’s shareholders. The Omnibus Plan permits the issuance of up to 1,500,000 shares of the Company’s common stock in the form of stock options, SARs, restricted stock, restricted stock units and performance awards.

All share and per share data have been restated to give effect to the 10% stock dividend issued on December 15, 2017.

Restricted Stock
Restricted shares granted prior to April 16, 2013 are amortized to expense over the three-year vesting period. Beginning on April 16, 2013, restricted shares granted to Company employees are amortized to expense over the three-year annual vesting period whereas restricted shares granted to members of the Board of Directors are amortized to expense over a one-year service period, with the exception of those shares granted in lieu of cash payment for retainer fees which are expensed in the period earned. Beginning on February 2, 2017, restricted shares granted to Company employees are amortized to expense over the three-year cliff vesting period.

Changes in restricted shares outstanding for the year ended December 31, 2017 were as follows:

			Weighted Average
			Grant Date
	Shares		Fair Value
Balance at December 31, 2016	81,269		$	46.39
Granted	26,064		$	59.46
Vested	(29,167	)	$	47.58
Forfeited	—			—
Balance at December 31, 2017	78,166		$	50.30

During 2016 and 2015, 39,816 and 47,065 shares, respectively, were granted with weighted average per share market values at date of grant of $45.75 in 2016 and $46.40 in 2015. The fair value of such shares, are based on the market price on the date of grant. Amortization of the restricted stock bonus awards totaled $1,743,000 for 2017, $1,712,000 for 2016 and $1,514,000 for 2015. As of December 31, 2017, the total unrecognized compensation expense related to non-vested restricted stock awards was $1,345,000 and the related weighted average period over which it is expected to be recognized is approximately 0.63 years. The total fair value of shares vested during the years ended December 2017, 2016, and 2015 was $1,550,000, $1,500,000, and $1,089,000, respectively.

Performance-Based Restricted Stock
In February 2017, the Company granted three-year performance-based restricted stock (“PBRS”) awards which are contingent upon the achievement of pre-established financial goals over the period from January 1, 2017 through December 31, 2019. The PBRS awards cliff vest on the three-year anniversary of their grant date at levels ranging from 0% to 150% of the target opportunity based on the actual achievement of financial goals for the three-year performance period. The target number of PBRS shares granted was 25,342 with a grant date fair value of $59.20 per share. The 2017 expense related to this grant totaled $579,000 and is based on the grant date fair value and the anticipated achievement of approximately 124% of the target financial goals. The estimated expense for 2018 and each future period through the vesting date is subject to prospective adjustment based upon changes in the expected achievement of the financial goals.

SARs
There were no SARs granted during the year ended December 31, 2017.

During 2017, the Company recognized SARs expense of $18,000. As of December 31, 2017, there was no unrecognized compensation expense related to SARs.

Changes in SARs outstanding for the year ended December 31, 2017 were as follows:

	SARs		Weighted Average Exercise Price
Balance at December 31, 2016	261,206		$	34.75
Exercised	(26,970	)		33.09
Forfeited	—			—
Balance at December 31, 2017	234,236			34.97
Exercisable at December 31, 2017	234,236		$	34.97

The total intrinsic value of SARs exercised during 2017 and 2016 was $892,000 and $2,162,000, respectively. The average remaining contractual term for SARs outstanding as of December 31, 2017 was 5.03 years, and the aggregate intrinsic value was $7,291,000. The average remaining contractual term for SARs exercisable as of December 31, 2016 was 5.22 years, and the aggregate intrinsic value was $8,395,000.

The total compensation cost for share-based payment arrangements was $2,340,000, $1,959,000, and $2,059,000 in 2017, 2016, and 2015, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

Note 13
Income Taxes

The components of income tax expense (benefit) are as follows:

	For the Years Ended December 31,
(In thousands)	2017			2016		2015
Current:
Federal	$	4,250		$	6,456	$	6,825
State		1,638			941		1,290
Deferred:
Federal		4,256			301		(84	)
State		(259	)		18		(53	)
Total income tax expense	$	9,885		$	7,716	$	7,978

A reconciliation of expected income tax expense (benefit), computed by applying the effective federal statutory rate of 35% for each of 2017, 2016 and 2015 to income before income tax expense is as follows:

	For the Years Ended December 31,
(In thousands)	2017			2016			2015
Expected income tax expense	$	12,214		$	11,223		$	10,862
(Reductions) increases resulting from:
Tax-exempt income		(3,868	)		(3,754	)		(3,704	)
State taxes, net of federal benefit		896			623			804
Share-based compensation adjustment		(376	)		—			—
Adjustment of deferred tax asset or liability for TCJA		1,824			—			—
Other, net		(805	)		(376	)		16
Total income tax expense	$	9,885		$	7,716		$	7,978

On December 22, 2017, the TCJA was enacted. Among other things, the new law (i) establishes a new, flat corporate federal statutory income tax rate of 21%; (ii) eliminates the corporate alternative minimum tax and allows the use of any such carryforwards to offset regular tax liability for any taxable year; (iii) limits the deduction for net interest expense incurred by U.S. corporations; (iv) allows businesses to immediately expense, for tax purposes, the cost of new investments in certain qualified depreciable assets; (v) eliminates or reduces certain deductions related to meals and entertainment expenses; (vi) modifies the limitation on excessive employee remuneration to eliminate the exception for performance-based compensation and clarifies the definition of a covered employee; and (vii) limits the deductibility of deposit insurance premiums. The TCJA also significantly changes U.S. tax law related to foreign operations, though, such changes do not currently impact the Company on a significant level.

Also on December 22, 2017, the SEC issued Staff Accounting Bulletin No. 118 (SAB 118), which provides guidance on accounting for tax effects of the TCJA. SAB 118 provides a measurement period of up to one year from the enactment date to complete the accounting. Based on the information available and current interpretation of the rules, the Company has made provisional estimates of the impact of the reduction in the corporate tax rate and remeasurement of certain deferred tax assets and liabilities based on the rate at which they are expected to reverse in the future. The final analysis and measurement will be completed during 2018 when the Company files the 2017 U.S. federal income tax return.

Income tax expense in 2017 totaled $9,885,000 compared to $7,716,000 and $7,978,000 in 2016 and 2015, respectively. When measured as a percent of pre-tax income, the Company’s effective tax rate was 28% in 2017, 24% in 2016, and 26% in 2015. The increase in 2017 tax expense was primarily the result of a one-time, non-cash charge of $1,824,000 triggered by the passage of the TCJA on December 22, 2017. The charge consists of the following:

●	The deferred tax inventory was revalued at the new rate of 21% and resulted in a net credit of $462,000.
●	AOCI related to pension and unrealized gains/losses on securities available for sale was revalued at the new rate of 21% and resulted in a net charge of $2,286,000.

The Company’s effective tax rate for 2017 including and excluding the one-time TCJA charge was 28% and 25%, respectively. As a result of the lower TCJA rates, the effective rate for 2018 is anticipated to decrease by approximately 25% vs. the 2017 rate excluding the TCJA charge. The Company’s effective tax rate has traditionally been lower than the statutory rate because of investments and loans that are tax exempt.

The tax effects of temporary differences which give rise to significant portions of the deferred tax assets and deferred tax liabilities are presented below:

	December 31,
(In thousands)	2017			2016
Deferred tax assets:
Allowance for loan losses	$	2,413		$	3,718
ASC 715 pension funding liability		6,080			8,969
Net operating loss carryforward⁽¹⁾		76			169
Supplemental executive retirement plan accrual		1,833			2,604
Stock compensation		1,307			1,695
Other		118			177
Total deferred tax assets	$	11,827		$	17,332
Deferred tax liabilities:
Premises and equipment		(2,248	)		(2,731	)
Pension		(1,379	)		(3,601	)
Intangible/assets		(1,091	)		(1,402	)
Unrealized gain on investment in securities available-for-sale		(1,938	)		(560	)
Deferred income		(2,121	)		—
Total deferred tax liabilities	$	(8,777	)	$	(8,294	)
Net deferred tax assets	$	3,050		$	9,038

⁽¹⁾

As of December 31, 2017, the Company had approximately $361,000 of net operating loss carry forwards as a result of the acquisition of Franklin Bancorp. The utilization of the net operating loss carry forward is subject to Section 382 of the Internal Revenue Code and limits the Company’s use to approximately $122,000 per year during the carry forward period, which expires in 2020.

A valuation allowance would be provided on deferred tax assets when it is more likely than not that some portion of the assets will not be realized. The Company has not established a valuation allowance at December 31, 2017 or 2016, due to management’s belief that all criteria for recognition have been met, including the expectation of projected future taxable income sufficient to support the realization of deferred tax assets.

The reconciliation of the beginning unrecognized tax benefits balance to the ending balance is presented in the following table:

(In thousands)	2017			2016			2015
Balance at January 1	$	1,623		$	1,194		$	1,117
Changes in unrecognized tax benefits as a result of tax positions taken during a prior year		(15	)		407			10
Changes in unrecognized tax benefits as a result of tax position taken during the current year		263			311			277
Decreases in unrecognized tax benefits relating to settlements with taxing authorities		—			—			—
Reductions to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations		(239	)		(289	)		(210	)
Balance at December 31	$	1,632		$	1,623		$	1,194

At December 31, 2017, 2016 and 2015, the balance of the Company’s unrecognized tax benefits which would, if recognized, affect the Company’s effective tax rate was $1,464,000, $1,225,000 and $861,000, respectively. These amounts are net of the offsetting benefits from other taxing jurisdictions.

As of December 31, 2017, 2016 and 2015, the Company had $139,000, $108,000 and $54,000, respectively, in accrued interest related to unrecognized tax benefits. During 2017 and 2016, the Company recorded a net increase in accrued interest of $31,000 and $54,000, respectively.

The Company believes it is reasonably possible that the total amount of tax benefits will decrease by approximately $299,000 over the next 12 months. The reduction primarily relates to the anticipated lapse in the statute of limitations. The unrecognized tax benefits relate primarily to apportionment of taxable income among various state tax jurisdictions.

The Company is subject to income tax in the U.S. federal jurisdiction, numerous state jurisdictions, and a foreign jurisdiction. The Company’s federal income tax returns for tax years 2014 through 2016 remain subject to examination by the Internal Revenue Service. In addition, the Company is subject to state tax examinations for the tax years 2013 through 2016.

Disclosures about Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Disclosures about Fair Value of Financial Instruments

Note 15
Disclosures about Fair Value of Financial Instruments

The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit, commercial letters of credit and standby letters of credit. The Company’s maximum potential exposure to credit loss in the event of nonperformance by the other party to the financial instrument for commitments to extend credit, commercial letters of credit and standby letters of credit is represented by the contractual amounts of those instruments. At December 31, 2017 and 2016, no amounts have been accrued for any estimated losses for these instruments.

Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commercial and standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. These off-balance sheet financial instruments generally have fixed expiration dates or other termination clauses and may require payment of a fee. The approximate remaining terms of commercial and standby letters of credit range from less than one to five years. Since these financial instruments may expire without being drawn upon, the total amounts do not necessarily represent future cash requirements. Commitments to extend credit and letters of credit are subject to the same underwriting standards as those financial instruments included on the consolidated balance sheets. The Company evaluates each customer’s credit-worthiness on a case-by-case basis. The amount of collateral obtained, if deemed necessary upon extension of the credit, is based on management’s credit evaluation of the borrower. Collateral held varies, but is generally accounts receivable, inventory, residential or income-producing commercial property or equipment. In the event of nonperformance, the Company may obtain and liquidate the collateral to recover amounts paid under its guarantees on these financial instruments.

The following table shows conditional commitments to extend credit, standby letters of credit and commercial letters:

	December 31,
(In thousands)	2017		2016
Conditional commitments to extend credit	$	87,013	$	45,497
Standby letters of credit		14,347		14,381
Commercial letters of credit		3,246		1,962

The fair value of commitments to extend credit and standby letters of credit is estimated using the fees currently charged to enter into similar agreements, taking into account the remaining terms of the agreements, the likelihood of the counterparties drawing on such financial instruments and the present credit worthiness of such counterparties. The Company believes such commitments have been made at terms which are competitive in the markets in which it operates; however, no premium or discount is offered thereon.

Following is a summary of the carrying amounts and fair values of the Company’s financial instruments:

	December 31,
	2017				2016
	Carrying				Carrying
(In thousands)	Amount		Fair Value		Amount		Fair Value
Balance sheet assets:
Cash and cash equivalents	$	228,110	$	228,110	$	266,743	$	266,743
Investment in securities		470,523		470,523		390,552		390,552
Loans, net		676,026		675,020		654,691		652,028
Accrued interest receivable		7,413		7,413		6,543		6,543
Total	$	1,382,072	$	1,381,066	$	1,318,529	$	1,315,866

Balance sheet liabilities:
Deposits	$	678,088	$	678,346	$	621,961	$	622,173
Accounts and drafts payable		661,888		661,888		642,287		642,287
Accrued interest payable		55		55		46		46
Total	$	1,340,031	$	1,340,289	$	1,264,294	$	1,264,506

The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value:

Cash and Cash Equivalents The carrying amount approximates fair value.

Investment in Securities The fair value is measured on a recurring basis using Level 2 valuations. Refer to Note 3, “Investment in Securities,” for fair value and unrealized gains and losses by investment type.

Loans The fair value is estimated using present values of future cash flows discounted at risk-adjusted interest rates for each loan category designated by management and is therefore a Level 3 valuation. Management believes that the risk factor embedded in the interest rates along with the allowance for loan losses results in a fair valuation.

Impaired loans are valued using the fair value of the collateral which is based upon an observable market price or current appraised value and therefore, the fair value is a nonrecurring Level 3 valuation.

Accrued Interest Receivable The carrying amount approximates fair value.

Deposits The fair value of demand deposits, savings deposits and certain money market deposits is the amount payable on demand at the reporting date. The fair value of fixed-maturity certificates of deposit is estimated using the rates currently offered for deposits of similar remaining maturities and therefore, is a Level 2 valuation. The fair value estimates above do not include the benefit that results from the low-cost funding provided by the deposit liabilities compared to the cost of borrowing funds in the market or the benefit derived from the customer relationship inherent in existing deposits.

Accounts and Drafts Payable The carrying amount approximates fair value.

Accrued Interest The carrying amount approximates fair value.

Limitations Fair value estimates are based on existing on- and off-balance sheet financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. Other significant assets or liabilities that are not considered financial assets or liabilities include premises and equipment and the benefit that results from the low-cost funding provided by the deposit liabilities compared to the cost of borrowing funds in the market (core deposit intangible). In addition, tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in any of the estimates.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

Industry Segment Information

Industry Segment Information

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Note 16
Industry Segment Information

The services provided by the Company are classified into two reportable segments: Information Services and Banking Services. Each of these segments provides distinct services that are marketed through different channels. They are managed separately due to their unique service, processing and capital requirements. The Information Services segment provides transportation, energy, telecommunication, and environmental invoice processing and payment services to large corporations. The Banking Services segment provides banking services primarily to privately held businesses and faith-based ministries.

The Company’s accounting policies for segments are the same as those described in Note 1 of this report. Management evaluates segment performance based on net income after allocations for corporate expenses and income taxes. Transactions between segments are accounted for at what management believes to be fair value.

Substantially all revenue originates from and all long-lived assets are located within the United States, and no revenue from any customer of any segment exceeds 10% of the Company’s consolidated revenue. Assets represent actual assets owned by Information Services and Banking Services and there is no allocation methodology used. Loans are sold by Banking Services to Information Services to create liquidity to keep the Bank’s loan to deposit ratio within policy limits. Segment interest from customers is the actual interest earned on the loans owned by Information Services and Banking Services, respectively.

Summarized information about the Company’s operations in each industry segment for the years ended December 31, 2017, 2016 and 2015, is as follows:

						Corporate,
	Information		Banking			Eliminations
(In thousands)	Services		Services			and Other			Total
*2017*
Fee revenue and other income:
Income from customers	$	93,804	$	1,708		$	—		$	95,512
Intersegment income (expense)		13,317		1,545			(14,862	)		—
Net interest income (expense) after provision for loan losses:
Income from customers		13,400		26,390			—			39,790
Intersegment income (expense)		—		—			—			—
Depreciation and amortization		3,784		150			118			4,052
Income taxes		4,326		5,559			—			9,885
Net income		13,597		11,417			—			25,014
Goodwill		12,433		136			—			12,569
Other intangible assets, net		1,996		—			—			1,996
Total assets	$	800,214	$	830,672		$	(27,677	)	$	1,603,209
*2016*
Fee revenue and other income:
Income from customers	$	84,612	$	1,524		$	—		$	86,136
Intersegment income (expense)		12,164		1,575			(13,739	)		—
Net interest income (expense) after provision for loan losses:
Income from customers		13,820		25,581			—			39,401
Intersegment income (expense)		2		(2	)		—			—
Depreciation and amortization		3,368		165			120			3,653
Income taxes		1,478		6,238			—			7,716
Net income		14,049		10,299			—			24,348
Goodwill		11,454		136			—			11,590
Other intangible assets, net		1,997		—			—			1,997
Total assets	$	763,999	$	756,164		$	(15,324	)	$	1,504,839
*2015*
Fee revenue and other income:
Income from customers	$	82,144	$	1,224		$	—		$	83,368
Intersegment income (expense)		10,078		1,648			(11,726	)		—
Net interest income (expense) after provision for loan losses:
Income from customers		14,598		22,851			—			37,449
Intersegment income (expense)		12		(12	)		—			—
Depreciation and amortization		3,164		151			101			3,416
Income taxes		2,818		5,160			—			7,978
Net income		14,635		8,421			—			23,056
Goodwill		11,454		136			—			11,590
Other intangible assets, net		2,405		—			—			2,405
Total assets	$	702,491	$	761,739		$	(8,724	)	$	1,455,506

Condensed Financial Information of Parent Company

12 Months Ended

Dec. 31, 2017

Condensed Financial Information of Parent Company Only Disclosure [Abstract]

Condensed Financial Information of Parent Company

Note 18
Condensed Financial Information of Parent Company

Following are the condensed balance sheets of the Company (parent company only) and the related condensed statements of income and cash flows.

	Condensed Balance Sheets
	December 31,
(In thousands)	2017		2016
Assets
Cash and due from banks	$	56,462	$	45,464
Short-term investments		48,324		107,898
Securities available-for-sale, at fair value		470,523		390,552
Loans, net		12,239		47,184
Investments in subsidiaries		113,681		101,824
Premises and equipment, net		20,927		20,375
Other assets		199,865		161,317
Total assets	$	922,021	$	874,614
Liabilities and Shareholders’ Equity
Liabilities:
Accounts and drafts payable	$	661,342	$	640,945
Other liabilities		35,533		25,415
Total liabilities		696,875		666,360
Total shareholders’ equity		225,146		208,254
Total liabilities and shareholders’ equity	$	922,021	$	874,614

	Condensed Statements of Income
	For the Years Ended December 31,
(In thousands)	2017		2016		2015
Income from subsidiaries:
Interest	$	—	$	2	$	12
Management fees		2,172		2,105		2,201
Income from subsidiaries		2,172		2,107		2,213
Information services revenue		93,133		83,543		78,488
Net interest income after provision		13,217		13,389		13,948
Gain on sales of investment securities		—		387		2,910
Other income		483		504		613
Total income		109,005		99,930		98,172
Expenses:
Salaries and employee benefits		70,409		65,968		63,475
Other expenses		20,333		18,133		16,580
Total expenses		90,742		84,101		80,055
Income before income tax and equity in undistributed income of subsidiaries		18,263		15,829		18,117
Income tax expense		4,394		1,540		2,950
Income before undistributed income of subsidiaries		13,869		14,289		15,167
Equity in undistributed income of subsidiaries		11,145		10,059		7,889
Net income	$	25,014	$	24,348	$	23,056

	Condensed Statements of Cash Flows
	For the Years Ended December 31,
(In thousands)	2017			2016			2015
Cash flows from operating activities:
Net income	$	25,014		$	24,348		$	23,056
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed income of subsidiaries		(11,145	)		(10,059	)		(7,889	)
Net change in other assets		(41,013	)		(7,085	)		16,100
Net change in other liabilities		10,118			6,683			(2,779	)
Amortization of stock-based awards		1,743			1,677			1,504
Other, net		9,219			7,558			10,389
Net cash (used in) provided by operating activities		(6,064	)		23,122			40,381
Cash flows from investing activities:
Net increase in securities		(80,621	)		(33,025	)		(23,472	)
Net decrease in loans		34,944			40,431			28,343
Purchases of premises and equipment, net		(4,020	)		(4,557	)		(5,708	)
Net cash (used in) provided by investing activities		(49,697	)		2,849			(837	)
Cash flows from financing activities:
Net increase (decrease) in accounts and drafts payable		20,397			64,026			(78,439	)
Cash dividends paid		(10,675	)		(9,979	)		(9,697	)
Purchase of common shares for treasury		(2,270	)		(9,215	)		(10,951	)
Other financing activities		(267	)		1,705			66
Net cash provided by (used in) financing activities		7,185			46,537			(99,021	)
Net increase (decrease) in cash and cash equivalents		(48,576	)		72,508			(59,477	)
Cash and cash equivalents at beginning of year		153,362			80,854			140,331
Cash and cash equivalents at end of year	$	104,786		$	153,362		$	80,854

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

Supplemental Income Statement Elements [Abstract]

SUPPLEMENTARY FINANCIAL INFORMATION

12 Months Ended

Dec. 31, 2017

SUPPLEMENTARY FINANCIAL INFORMATION

Note 19
SUPPLEMENTARY FINANCIAL INFORMATION
(Unaudited)

	First			Second		Third		Fourth
(In thousands except per share data)	Quarter			Quarter		Quarter		Quarter			YTD
*2017*
Fee revenue and other income	$	22,771		$	23,800	$	24,207	$	24,734		$	95,512
Interest income		9,999			10,332		10,665		10,981			41,977
Interest expense		480			470		571		666			2,187
Net interest income		9,519			9,862		10,094		10,315			39,790
Provision for loan losses		—			—		—		—			—
Operating expense		24,318			24,901		25,042		26,142			100,403
Income tax expense		1,665			2,248		2,396		3,576	*		9,885	*
Net income	$	6,307		$	6,513	$	6,863	$	5,331		$	25,014
Net income per share:
Basic earnings per share	$	.51		$	.53	$	.56	$	.44		$	2.04
Diluted earnings per share		.51			.52		.55		.43			2.01
*2016*
Fee revenue and other income	$	20,505		$	21,457	$	22,149	$	22,025		$	86,136
Interest income		9,777			10,010		9,985		10,158			39,930
Interest expense		513			504		505		507			2,029
Net interest income		9,264			9,506		9,480		9,651			37,901
Provision for loan losses		(1,000	)		—		—		(500	)		(1,500	)
Operating expense		22,916			23,059		23,552		23,946			93,473
Income tax expense		2,020			2,035		1,855		1,806			7,716
Net income	$	5,833		$	5,869	$	6,222	$	6,424		$	24,348
Net income per share:
Basic earnings per share	$	.47		$	.48	$	.51	$	.53		$	1.99
Diluted earnings per share		.47			.47		.50		.52			1.96

⁽¹⁾ Includes one-time, non-cash TCJA charge of $1,824,000

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Operations	*Summary of Operations* Cass Information Systems, Inc. (the “Company”) provides payment and information services, which include processing and payment of transportation, energy, telecommunications and environmental invoices. These services include the acquisition and management of data, information delivery and financial exchange. The consolidated balance sheet captions, “Accounts and drafts payable” and “Payments in excess of funding,” represent the Company’s resulting financial position related to the payment services that are performed for customers. The Company also provides a full range of banking services to individual, corporate and institutional customers through Cass Commercial Bank (the “Bank”), its wholly owned bank subsidiary.
Basis of Presentation	*Basis of Presentation* The accounting and reporting policies of the Company and its subsidiaries conform to U.S. generally accepted accounting principles (“GAAP”). The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries after elimination of intercompany transactions. Certain amounts in the 2016 and 2015 consolidated financial statements have been reclassified to conform to the 2017 presentation. Such reclassifications have no effect on previously reported net income or shareholders’ equity. The Company issued a 10% stock dividend on December 15, 2017. The share and per share information have been restated unless indicated otherwise for all periods presented in the accompanying consolidated financial statements.
Use of Estimates	*Use of Estimates* In preparing the consolidated financial statements, Company management is required to make estimates and assumptions which significantly affect the reported amounts in the consolidated financial statements.
Cash and Cash Equivalents	*Cash and Cash Equivalents* For purposes of the consolidated statements of cash flows, the Company considers cash and due from banks, interest-bearing deposits in other financial institutions, federal funds sold and other short-term investments as segregated in the accompanying consolidated balance sheets to be cash equivalents.
Investment in Debt Securities	*Investment in Debt Securities* The Company classifies its debt marketable securities as available-for-sale. Securities classified as available-for-sale are carried at fair value. Unrealized gains and losses, net of the related tax effect, are excluded from earnings and reported in accumulated other comprehensive income, a component of shareholders’ equity. A decline in the fair value of any available-for-sale security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. To determine whether impairment is other than temporary, the Company considers guidance provided in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320 - Investments – Debt and Equity Securities. When determining whether a debt security is other-than-temporarily impaired, the Company assesses whether it has the intent to sell the security and whether it is more likely than not that the Company will be required to sell prior to recovery of the amortized cost basis. Evidence considered in this assessment includes the reasons for impairment, the severity and duration of the impairment, changes in value subsequent to year-end and forecasted performance of the investee. Premiums and discounts are amortized or accreted to interest income over the estimated lives of the securities using the level-yield method. Interest income is recognized when earned. Gains and losses are calculated using the specific identification method.
Allowance for Loan Losses	*Allowance for Loan Losses (“ALLL”)* The ALLL is increased by provisions charged to expense and is available to absorb charge-offs, net of recoveries. Management utilizes a systematic, documented approach in determining the appropriate level of the ALLL. Management’s approach provides for estimated credit losses on individually evaluated loans in accordance with FASB ASC 310 - Allowance for Credit Losses (“ASC 310”). These estimates are based upon a number of factors, such as payment history, financial condition of the borrower, expected future cash flows and discounted collateral exposure. Estimated credit losses inherent in the remainder of the portfolio are estimated in accordance with FASB ASC 450 -Contingencies. These loans are segmented into groups based on similar risk characteristics. Historical loss rates for each risk group, which are updated quarterly, are generally quantified using all recorded loan charge-offs and recoveries over a prescribed look-back period. These historical loss rates for each risk group are used as the starting point to determine the level of the allowance. The Company’s methodology incorporates an estimated loss emergence period for each risk group. The loss emergence period is the period of time from when a borrower experiences a loss event and when the actual loss is recognized in the financial statements, generally at the time of initial charge-off of the loan balance. The Company’s methodology also includes qualitative risk factors that allow management to adjust its estimates of losses based on the most recent information available and to address other limitations in the quantitative component that is based on historical loss rates. Such risk factors are generally reviewed and updated quarterly, as appropriate, and are adjusted to reflect changes in national and local economic conditions and developments, the volume and severity of delinquent and internally classified loans, loan concentrations, assessment of trends in collateral values, assessment of changes in borrowers’ financial stability, and changes in lending policies and procedures, including underwriting standards and collections, charge-off and recovery practices. Management believes the ALLL is adequate to absorb probable losses in the loan portfolio. Additionally, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s ALLL. Such agencies may require the Company to increase the ALLL based on their judgments and interpretations about information available to them at the time of their examinations.
Premises and Equipment	*Premises and Equipment* Premises and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is computed over the estimated useful lives of the assets, or the respective lease terms for leasehold improvements, using straight-line and accelerated methods. Estimated useful lives do not exceed 40 years for buildings, the lesser of 10 years or the life of the lease for leasehold improvements and range from 3 to 7 years for software, equipment, furniture and fixtures. Maintenance and repairs are charged to expense as incurred.
Intangible Assets	*Intangible Assets* Cost in excess of fair value of net assets acquired has resulted from business acquisitions. Goodwill and intangible assets with indefinite useful lives are not amortized, but instead are tested for impairment at least annually. Intangible assets with definite useful lives are amortized on a straight-line basis over their respective estimated useful lives. Periodically, the Company reviews intangible assets for events or changes in circumstances that may indicate that the carrying amount of the assets may not be recoverable. Based on those reviews, adjustments of recorded amounts have not been required.
Non-marketable Equity Investments	*Non-marketable Equity Investments* The Company accounts for non-marketable equity investments, in which it holds less than a 20% ownership, under the cost method. Under the cost method of accounting, investments are carried at cost and are adjusted only for other than temporary declines in fair value, distributions of earnings and additional investments. The Company periodically evaluates whether any declines in fair value of its investments are other than temporary. In performing this evaluation, the Company considers various factors including any decline in market price, where available, the investee's financial condition, results of operations, operating trends and other financial ratios. Non-marketable equity investments are included in other assets on the consolidated balance sheets.
Foreclosed Assets	*Foreclosed Assets* Real estate acquired as a result of foreclosure is initially recorded at fair value less estimated selling costs. Fair value is generally determined through the receipt of appraisals. Any write down to fair value at the time the property is acquired is recorded as a charge-off to the allowance for loan losses. Any decline in the fair value of the property subsequent to acquisition is recorded as a charge to non-interest expense.
Treasury Stock	*Treasury Stock* Purchases of the Company’s common stock are recorded at cost. Upon reissuance, treasury stock is reduced based upon the average cost basis of shares held.
Comprehensive Income	*Comprehensive Income* Comprehensive income consists of net income, changes in net unrealized gains (losses) on available-for-sale securities and pension liability adjustments and is presented in the accompanying consolidated statements of shareholders' equity and consolidated statements of comprehensive income.
Loans	*Loans* Interest on loans is recognized based upon the principal amounts outstanding. It is the Company’s policy to discontinue the accrual of interest when there is reasonable doubt as to the collectability of principal or interest. Subsequent payments received on such loans are applied to principal if there is any doubt as to the collectability of such principal; otherwise, these receipts are recorded as interest income. The accrual of interest on a loan is resumed when the loan is current as to payment of both principal and interest and/or the borrower demonstrates the ability to pay and remain current. Loan origination and commitment fees on originated loans, net of certain direct loan origination costs, are deferred and amortized to interest income using the level-yield method over the estimated lives of the related loans.
Impairment of Loans	*Impairment of Loans* A loan is considered impaired when it is probable that a creditor will be unable to collect all amounts due, both principal and interest, according to the contractual terms of the loan agreement. When measuring impairment, the expected future cash flows of an impaired loan are discounted at the loan's effective interest rate. Alternatively, impairment could be measured by reference to an observable market price, if one exists, or the fair value of the collateral for a collateral-dependent loan. Regardless of the historical measurement method used, the Company measures impairment based on the fair value of the collateral when the Company determines foreclosure is probable. Additionally, impairment of a restructured loan is measured by discounting the total expected future cash flows at the loan's effective rate of interest as stated in the original loan agreement. The Company uses its nonaccrual methods as discussed above for recognizing interest on impaired loans.
Information Services Revenue	*Information Services Revenue* A majority of the Company’s revenues are attributable to fees for providing services. These services include transportation invoice rating, payment processing, auditing, and the generation of accounting and transportation information. The Company also processes, pays and generates management information from electric, gas, telecommunications, environmental, and other invoices. The specific payment and information processing services provided to each customer are developed individually to meet each customer’s specific requirements. The Company enters into service agreements with customers typically for fixed fees per transaction that are invoiced monthly. Revenues are recognized in the period services are rendered and earned under the service agreements, as long as collection is reasonably assured.
Income Taxes	*Income Taxes* Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. Deferred tax assets are reduced if necessary, by a deferred tax asset valuation allowance. In the event that management determines it is more likely than not that it will not be able to realize all or part of net deferred tax assets in the future, the Company adjusts the recorded value of deferred tax assets, which would result in a direct charge to income tax expense in the period that such determination is made. Likewise, the Company will reverse the valuation allowance when realization of the deferred tax asset is expected. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.
Earnings Per Share	*Earnings Per Share* Basic earnings per share is computed by dividing net income by the weighted average number of common shares outstanding. Diluted earnings per share is computed by dividing net income by the sum of the weighted average number of common shares outstanding and the weighted average number of potential common shares outstanding.
Share-Based Compensation	*Stock-Based Compensation* The Company follows FASB ASC 718 - Accounting for Stock Options and Other Stock-based Compensation (“ASC 718”), which requires that all stock-based compensation be recognized as an expense in the financial statements and that such cost be measured at the fair value of the award. FASB ASC 718 also requires that excess tax benefits related to stock option exercises and restricted stock awards be reflected as financing cash inflows instead of operating cash inflows.
Pension Plans	*Pension Plans* The amounts recognized in the consolidated financial statements related to pension are determined from actuarial valuations. Inherent in these valuations are assumptions including expected return on plan assets, discount rates at which the liabilities could be settled at December 31, 2017, rate of increase in future compensation levels and mortality rates. These assumptions are updated annually and are disclosed in Note 10. The Company follows FASB ASC 715 - Compensation – Retirement Benefits (“ASC 715”), which requires companies to recognize the overfunded or underfunded status of a defined benefit postretirement plan as an asset or liability in its consolidated balance sheet and to recognize changes in that funded status in the year in which the changes occur through comprehensive income. The funded status is measured as the difference between the fair value of the plan assets and the projected benefit obligation as of the date of its fiscal year-end.
Fair Value Measurements	*Fair Value Measurements* The Company follows the provisions of FASB ASC 820 - Fair Value Measurements and Disclosures, which defines fair value, establishes a framework for measuring fair value in GAAP, and outlines disclosures about fair value measurements. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. A three-level hierarchy for valuation techniques is used to measure financial assets and financial liabilities at fair value. This hierarchy is based on whether the valuation inputs are observable or unobservable. Financial instrument valuations are considered Level 1 when they are based on quoted prices in active markets for identical assets or liabilities. Level 2 financial instrument valuations use quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Financial instrument valuations are considered Level 3 when they are determined using pricing models, discounted cash flow methodologies or similar techniques and at least one significant model assumption or input is unobservable, and when determination of the fair value requires significant management judgment or estimation. The Company records securities available for sale at their fair values on a recurring basis using Level 2 valuations. Additionally, the Company records impaired loans and other real estate owned at their fair value on a nonrecurring basis. The nonrecurring fair value adjustments typically involve application of lower-of-cost-or-market accounting or impairment write-downs of individual assets.
Impact of New and Not Yet Adopted Accounting Pronouncements	Impact of New and Not Yet Adopted Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update (“ASU”) No. 2014-09 – Revenue from Contracts with Customers. The ASU supersedes revenue recognition requirements in Topic 605, Revenue Recognition, including most industry-specific revenue recognition guidance in the FASB Accounting Standards Codification (“ASC”). The core principle of the new guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance identifies specific steps that entities should apply in order to achieve this principle. Under the ASU, the amendments are effective for interim and annual periods beginning January 1, 2018 and must be applied retrospectively. The Company’s revenue is comprised of net interest income on financial assets and liabilities, which is explicitly excluded from the scope, and non-interest income. The Company will use the modified retrospective transition approach and there will not be a significant impact on the Company’s consolidated financial statements or results of operations. In January 2016, the FASB issued ASU No. 2016-01 – Financial Instruments – Overall (ASC Subtopic 825-10). The ASU requires an entity to: (i) measure equity investments at fair value through net income, with certain exceptions; (ii) present in OCI the changes in instrument-specific credit risk for financial liabilities measured using the fair value option; (iii) present financial assets and financial liabilities by measurement category and form of financial asset; (iv) calculate the fair value of financial instruments for disclosure purposes based on an exit price and; (v) assess a valuation allowance on deferred tax assets related to unrealized losses of AFS debt securities in combination with other deferred tax assets. The standard is effective for fiscal periods beginning January 1, 2018 and will not have a significant impact on the Company’s consolidated financial statements or results of operations. In February 2016, the FASB issued ASU No. 2016-02 – Leases (ASC Topic 842). The ASU improves financial reporting about leasing transactions. The ASU affects all companies and other organizations that lease assets such as real estate, airplanes, and manufacturing equipment. Consistent with current generally accepted accounting principles (GAAP), the recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily will depend on its classification as a finance or operating lease. However, unlike current GAAP—which requires only capital leases to be recognized on the balance sheet—the new ASU will require both types of leases to be recognized on the balance sheet. The ASU also will require disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. These disclosures include qualitative and quantitative requirements, providing additional information about the amounts recorded in the financial statements. The ASU on leases will take effect for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. A third-party vendor solution has been selected to assist in the application of ASU 2016-02. The impact of the adoption of this ASU is currently being evaluated but is not expected to have a material impact on the Company’s consolidated financial statements or results of operations. In June 2016, the FASB issued ASU No. 2016-13 - Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The ASU requires measurement and recognition of expected credit losses for financial assets held. Under this standard, it will be required to hold an allowance equal to the expected life-of-loan losses on the loan portfolio. The standard is effective for fiscal periods beginning after December 15, 2019. The impact of the adoption of this ASU is currently being evaluated. In February 2018, the FASB issued ASU No. 2018-02 – Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The ASU provides for the reclassification of the effect of remeasuring deferred tax balances related to items within AOCI to retained earnings resulting from the TCJA. The Company early adopted, and as a result, reclassified $2,286,000 from AOCI to retained earnings.

Capital Requirements and Regulatory Restrictions (Tables)

12 Months Ended

Dec. 31, 2017

Regulatory Capital Requirements [Abstract]

Schedule of Capital Amounts and Ratios

The Company’s and the Bank’s actual and required capital amounts and ratios are as follows:

					Capital				Requirement to be
	Actual				Requirements				Well-Capitalized
(In thousands)	Amount		Ratio		Amount		Ratio		Amount		Ratio
At December 31, 2017
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	234,389	22.53	%	$	83,233	8.00	%	$	N/A	N/A	%
Cass Commercial Bank		122,440	17.01			57,568	8.00			71,960	10.00
Common Equity Tier I Capital (to risk-weighted assets)
Cass Information Systems, Inc.		224,184	21.55			46,819	4.50			N/A	N/A
Cass Commercial Bank		114,603	15.93			32,382	4.50			46,774	6.50
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		224,184	21.55			62,425	6.00			N/A	N/A
Cass Commercial Bank		114,603	15.93			43,176	6.00			57,568	8.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		224,184	13.87			64,649	4.00			N/A	N/A
Cass Commercial Bank		114,603	14.99			30,581	4.00			38,227	5.00
At December 31, 2016
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	219,747	22.75	%	$	77,272	8.00	%	$	N/A	N/A	%
Cass Commercial Bank		110,576	16.72			52,898	8.00			66,123	10.00
Common Equity Tier I Capital (to risk-weighted assets)
Cass Information Systems, Inc.		209,572	21.70			43,466	4.50			N/A	N/A
Cass Commercial Bank		102,769	15.54			29,755	4.50			42,980	6.50
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		209,572	21.70			57,954	6.00			N/A	N/A
Cass Commercial Bank		102,769	15.54			39,674	6.00			52,898	8.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		209,572	13.83			60,620	4.00			N/A	N/A
Cass Commercial Bank		102,769	13.98			29,409	4.00			36,761	5.00

Investment in Securities (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities

The amortized cost, gross unrealized gains, gross unrealized losses and fair value of debt and equity securities are summarized as follows:

	December 31, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized
(In thousands)	Cost		Gains		Losses		Fair Value
State and political subdivisions	$	408,165	$	9,528	$	661	$	417,032
U.S. government agencies		46,222		—		722		45,500
Certificates of deposit		7,991		—		—		7,991
Total	$	462,378	$	9,528	$	1,383	$	470,523

	December 31, 2016
			Gross		Gross
	Amortized		Unrealized		Unrealized
(In thousands)	Cost		Gains		Losses		Fair Value
State and political subdivisions	$	368,223	$	5,239	$	3,328	$	370,134
U.S. government agencies		13,075		—		403		12,672
Certificates of deposit		7,746		—		—		7,746
Total	$	389,044	$	5,239	$	3,731	$	390,552

Schedule of Fair Value of Securities with Unrealized Losses

The fair values of securities with unrealized losses are as follows:


					December 31, 2017
	Less than 12 months				12 months or more				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
(In thousands)	Fair Value		Losses		Fair Value		Losses		Fair value		Losses
State and political subdivisions	$	34,755	$	123	$	31,251	$	538	$	66,006	$	661
U.S. government agencies		34,183		376		11,317		346		45,500		722
Certificates of deposit		—		—		—		—		—		—
Total	$	68,938	$	499	$	42,568	$	884	$	111,506	$	1,383

					December 31, 2016
	Less than 12 months				12 months or more				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
(In thousands)	Fair Value		Losses		Fair Value		Losses		Fair value		Losses
State and political subdivisions	$	140,384	$	3,328	$	—	$	—	$	140,384	$	3,328
U.S. government agencies		12,672		403		—		—		12,672		403
Certificates of deposit		—		—		—		—		—		—
Total	$	153,056	$	3,731	$	—	$	—	$	153,056	$	3,731

Schedule of Amortized Cost and Fair Value

	December 31, 2017
(In thousands)	Amortized Cost		Fair Value
Due in 1 year or less	$	22,492	$	22,638
Due after 1 year through 5 years		57,922		58,425
Due after 5 years through 10 years		256,396		263,961
Due after 10 years		125,568		125,499
No stated maturity		—		—
Total	$	462,378	$	470,523

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

Summary of Loan Categories

Loans (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

A summary of loan categories is as follows:

	December 31,
(In thousands)	2017		2016
Commercial and industrial	$	236,394	$	214,767
Real estate
Commercial:
Mortgage		94,675		104,779
Construction		9,359		6,325
Church, church-related:
Mortgage		316,073		321,168
Construction		25,948		11,152
Industrial Revenue Bonds		3,374		6,639
Other		408		36
Total loans	$	686,231	$	664,866

Schedule of the Aging Loans by Loan Categories

The following table presents the aging of loans by loan categories at December 31, 2017:

	Performing						Nonperforming
							90 Days
			30-59		60-89		and		Non-		Total
(In thousands)	Current		Days		Days		Over		accrual		Loans
Commercial and industrial	$	236,394	$	—	$	—	$	—	$	—	$	236,394
Real estate
Commercial:
Mortgage		94,675		—		—		—		—		94,675
Construction		9,359		—		—		—		—		9,359
Church, church-related:
Mortgage		316,073		—		—		—		—		316,073
Construction		25,948		—		—		—		—		25,948
Industrial Revenue Bonds		3,374		—		—		—		—		3,374
Other		408		—		—		—		—		408
Total	$	686,231	$	—	$	—	$	—	$	—	$	686,231

The following table presents the aging of loans by loan categories at December 31, 2016:

	Performing						Nonperforming
							90 Days
			30-59		60-89		and		Non-		Total
(In thousands)	Current		Days		Days		Over		accrual		Loans
Commercial and industrial	$	214,767	$	—	$	—	$	—	$	—	$	214,767
Real estate
Commercial:
Mortgage		104,534		—		—		—		245		104,779
Construction		6,325		—		—		—		—		6,325
Church, church-related:
Mortgage		321,168		—		—		—		—		321,168
Construction		11,152		—		—		—		—		11,152
Industrial Revenue Bonds		6,639		—		—		—		—		6,639
Other		24		12		—		—		—		36
Total	$	664,609	$	12	$	—	$	—	$	245	$	664,866

Schedule of Credit Exposure of the Loan Portfolio

The following table presents the credit exposure of the loan portfolio by internally assigned credit grade as of December 31, 2017:

	Loans		Performing		Nonperforming
	Subject to		Loans Subject to		Loans Subject
	Normal		Special		to Special
(In thousands)	Monitoring⁽¹⁾		Monitoring⁽²⁾		Monitoring⁽²⁾		Total Loans
Commercial and industrial	$	234,271	$	2,123	$	—	$	236,394
Real estate
Commercial:
Mortgage		93,788		887		—		94,675
Construction		9,359		—		—		9,359
Church, church-related:
Mortgage		316,042		31		—		316,073
Construction		25,948		—		—		25,948
Industrial Revenue Bonds		3,374		—		—		3,374
Other		408		—		—		408
Total	$	683,190	$	3,041	$	—	$	686,231

^⁽¹⁾	Loans subject to normal monitoring involve borrowers of acceptable-to-strong credit quality and risk, who have the apparent ability to satisfy their loan obligation.
^{^{^⁽²⁾}}	Loans subject to special monitoring possess some credit deficiency or potential weakness which requires a high level of management attention.

The following table presents the credit exposure of the loan portfolio by internally assigned credit grade as of December 31, 2016:

	Loans		Performing		Nonperforming
	Subject to		Loans Subject to		Loans Subject to
	Normal		Special		Special
(In thousands)	Monitoring⁽¹⁾		Monitoring⁽²⁾		Monitoring⁽²⁾		Total Loans
Commercial and industrial	$	213,024	$	1,743	$	—	$	214,767
Real estate
Commercial:
Mortgage		103,778		756		245		104,779
Construction		6,325		—		—		6,325
Church, church-related:
Mortgage		318,030		3,138		—		321,168
Construction		11,152		—		—		11,152
Industrial Revenue Bonds		6,639		—		—		6,639
Other		36		—		—		36
Total	$	658,984	$	5,637	$	245	$	664,866

⁽¹⁾	Loans subject to normal monitoring involve borrowers of acceptable-to-strong credit quality and risk, who have the apparent ability to satisfy their loan obligation.
⁽²⁾	Loans subject to special monitoring possess some credit deficiency or potential weakness which requires a high level of management attention.

Schedule of Recorded Investment and Unpaid Principal Balance for Impaired Loans

The following table presents the recorded investment and unpaid principal balance for impaired loans at December 31, 2016:


					Related
			Unpaid		Allowance
	Recorded		Principal		for Loan
(In thousands)	Investment		Balance		Losses
Commercial and industrial:
Nonaccrual	$	—	$	—	$	—
Real estate
Commercial – Mortgage:
Nonaccrual		245		245		—
Church – Mortgage:
Nonaccrual		—		—		—
Total impaired loans	$	245	$	245	$	—

Summary of the Allowance for Loan Losses

A summary of the activity in the allowance for loan losses is as follows:

	December 31,		Charge-							December 31,
(In thousands)	2016		Offs		Recoveries		Provision			2017
Commercial and industrial	$	3,261	$	—	$	30	$	361		$	3,652
Real estate
Commercial:
Mortgage		1,662		—		—		(268	)		1,394
Construction		47		—		—		23			70
Church, church-related:
Mortgage		4,027		—		—		(65	)		3,962
Construction		85		—		—		111			196
Industrial Revenue Bond		101		—		—		(49	)		52
Other		992		—		—		(113	)		879
Total	$	10,175	$	—	$	30	$	—		$	10,205

Premises and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Summary of Premises and Equipment

A summary of premises and equipment is as follows:

	December 31,
(In thousands)	2017		2016
Land	$	873	$	873
Buildings		13,386		13,087
Leasehold improvements		2,120		2,098
Furniture, fixtures and equipment		14,801		13,248
Purchased software		4,819		4,704
Internally developed software		16,485		14,377
		52,484		48,387
Less accumulated depreciation		30,898		27,301
Total	$	21,586	$	21,086

Schedule of Future Minimum Rental Payments for Operating Leases

(In thousands)	Amount
2018	$	1,518
2019		1,270
2020		1,245
2021		1,118
2022		1,086
2023		226
Total	$	6,463

Acquired Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Company's Intangible Assets

Details of the Company’s intangible assets are as follows:

	December 31, 2017					December 31, 2016
	Gross Carrying		Accumulated			Gross Carrying		Accumulated
(In thousands)	Amount		Amortization			Amount		Amortization
Assets eligible for amortization:
Customer lists	$	4,288	$	(2,702	)	$	3,933	$	(2,342	)
Patent		72		(12	)		72		(8	)
Non-compete agreements		332		(291	)		261		(261	)
Software		234		(234	)		234		(234	)
Other		500		(191	)		500		(158	)
Unamortized intangible assets:
Goodwill⁽¹⁾		12,796		(227	)		11,817		(227	)
Total intangible assets	$	18,222	$	(3,657	)	$	16,817	$	(3,230	)

⁽¹⁾

Amortization through December 31, 2001 prior to adoption of FASB ASC 350.

Interest-Bearing Deposits (Tables)

12 Months Ended

Dec. 31, 2017

Interest-Bearing Deposits [Abstract]

Schedule of Interest Bearing Deposits

Interest-bearing deposits consist of the following:

	December 31,
(In thousands)	2017			2016
Interest-bearing demand deposits	$	332,881		$	322,091
Savings deposits		11,168			29,430
Time deposits:
Less than $100		2,658			3,523
$100 to less than $250		33,385			37,179
$250 or more		16,455			15,082
Total	$	396,547		$	407,305
Weighted average interest rate		.56	%		.48	%

Schedule of Interest on Deposits

Interest on deposits consists of the following:

	December 31,
(In thousands)	2017		2016		2015
Interest-bearing demand deposits	$	1,611	$	1,387	$	1,392
Savings deposits		79		100		65
Time deposits:
Less than $100		234		274		346
$100 to less than $250		114		191		119
$250 or more		149		77		189
Total	$	2,187	$	2,029	$	2,111

Schedule of Maturities of Time Deposits

The scheduled maturities of time deposits are summarized as follows:

	December 31,
	2017				2016
			Percent				Percent
(In thousands)	Amount		of Total		Amount		of Total
Due within:
One year	$	48,370	92.1	%	$	48,740	87.4	%
Two years		281	0.5			4,752	8.5
Three years		2,383	4.5			155	0.3
Four years		25	0.1			2,072	3.7
Five years		1,439	2.8			65	0.1
Total	$	52,498	100.0	%	$	55,784	100.0	%

Common Stock and Earnings per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Common Stock Outstanding

The table below shows activity in the outstanding shares of the Company’s common stock during 2017.

	2017
Shares outstanding at January 1	11,188,466
10% stock dividend issued December 15, 2017	1,116,711
Issuance of common stock:
Employee restricted stock grants	3,825
Employee SARs exercised	7,547
Directors’ compensation	8,389
Shares repurchased	(38,042	)
Shares outstanding at December 31	12,286,896

Schedule of the Calculations of Basic and Diluted Earnings per Share

The calculations of basic and diluted earnings per share are as follows:

	December 31,
(In thousands except share and per share data)	2017		2016		2015
Basic:
Net income	$	25,014	$	24,348	$	23,056
Weighted average common shares outstanding		12,250,465		12,265,434		12,494,466
Basic earnings per share	$	2.04	$	1.99	$	1.85
Diluted:
Net income	$	25,014	$	24,348	$	23,056
Weighted average common shares outstanding		12,250,465		12,265,434		12,494,466
Effect of dilutive restricted stock, PBRS and SARs		179,445		172,386		175,784
Weighted average common shares outstanding assuming dilution		12,429,910		12,437,820		12,670,250
Diluted earnings per share	$	2.01	$	1.96	$	1.82

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Projected Benefit Obligation

A summary of the activity in the Plan’s projected benefit obligation, assets, funded status and amounts recognized in the Company’s consolidated balance sheets is as follows:

(In thousands)	2017			2016
Projected benefit obligation:
Balance, January 1	$	85,551		$	78,369
Service cost		3,733			3,559
Interest cost		3,621			3,505
Actuarial (gain) loss		7,916			2,003
Benefits paid		(2,031	)		(1,885	)
Balance, December 31	$	98,790		$	85,551
Plan assets:
Fair value, January 1	$	73,168		$	71,174
Actual return		10,290			3,879
Employer contribution		—			—
Benefits paid		(2,031	)		(1,885	)
Fair value, December 31	$	81,427		$	73,168
Funded status:
Accrued pension liability	$	(17,363	)	$	(12,383	)

Schedule of Assumptions used to Determine Projected Benefit Obligation

	2017		2016		2015
Weighted average discount rate	3.75	%	4.25	%	4.50	%
Rate of increase in compensation levels	(a)		(a)		(a)

(a)	6.0% graded down to 3.25% over the first seven years of service

Schedule of Expected Pension Benefit Payments

The following pension benefit payments, which reflect expected future service, as appropriate, are expected to be paid by the Plan:

	Amount
2018	$	2,679,000
2019		2,823,000
2020		3,045,000
2021		3,300,000
2022		3,693,000
2023-2027		23,682,000

Schedule of Plan's Pension Costs

The Plan’s pension cost included the following components:

	For the Year Ended
	December 31,
(In thousands)	2017			2016			2015
Service cost – benefits earned during the year	$	3,733		$	3,559		$	3,796
Interest cost on projected benefit obligations		3,621			3,505			3,178
Expected return on plan assets		(4,681	)		(4,734	)		(4,864	)
Net amortization and deferral		1,382			1,259			1,542
Net periodic pension cost	$	4,055		$	3,589		$	3,652

Schedule of Assumptions used to Determine Net Pension Cost

The following represent the major assumptions used to determine the net pension cost of the Plan:

	2017		2016		2015
Weighted average discount rate	4.25	%	4.50	%	4.00	%
Rate of increase in compensation levels	(a)		(a)		(a)
Expected long-term rate of return on assets	6.50	%	6.75	%	6.75	%

(a)	6.0% graded down to 3.25% over the first seven years of service

Schedule of Assumed Long-term Rate of Return on Assets

The expected one-year nominal returns and annual standard deviations are shown by asset class below:

			One-Year Nominal		Annual Standard
Asset Class	% of Total Portfolio		Return		Deviation
Core Fixed Income	51	%	4.55	%	4.55	%
Large Cap U.S. Equities	14	%	7.00	%	15.85	%
Small Cap U.S. Equities	5	%	8.10	%	19.70	%
International (Developed)	25	%	7.99	%	17.93	%
International (Emerging)	5	%	10.56	%	27.35	%

Summary of the Fair Value Measurements by Type of Asset

A summary of the fair value measurements by type of asset is as follows:

	Fair Value Measurements as of December 31,
	2017						2016
			Quoted Prices						Quoted Prices
			in Active						in Active
			Markets for		Significant				Markets for		Significant
			Identical		Observable				Identical		Observable
			Assets		Inputs				Assets		Inputs
(In thousands)	Total		(Level 1)		(Level 2)		Total		(Level 1)		(Level 2)
Cash	$	374	$	374	$	—	$	340	$	340	$	—
Equity securities
U.S. Large Cap Growth		—		—		—		13,306		—		13,306
U.S. Small/Mid Cap Growth		4,111		—		4,111		5,655		—		5,655
Non-U. S. Core		21,065		—		21,065		10,588		—		10,588
U.S. Large Cap Passive		11,717		—		11,717		7,364		—		7,364
Emerging Markets		4,052		—		4,052		652		—		652
Fixed Income
U.S. Core		11,284		—		11,284		24,438		—		24,438
U.S. Passive		24,345		—		24,345		9,571		—		9,571
Opportunistic		4,479				4,479		1,254				1,254
Total	$	81,427	$	374	$	81,053	$	73,168	$	340	$	72,828

Supplemental Executive Retirement Plan [Member]

Summary of Projected Benefit Obligation

A summary of the activity in the SERP’s projected benefit obligation, funded status and amounts recognized in the Company’s consolidated balance sheets is as follows:

	December 31,
(In thousands)	2017			2016
Benefit obligation:
Balance, January 1	$	9,132		$	8,748
Service cost		143			133
Interest cost		360			367
Benefits paid		(247	)		(247	)
Actuarial (gain) loss		706			131
Balance, December 31	$	10,094		$	9,132

Schedule of Assumptions used to Determine Projected Benefit Obligation

	2017		2016		2015
Weighted average discount rate	3.50	%	4.00	%	4.25	%
Rate of increase in compensation levels	(a)		(a)		(a)

(a)	6.00% graded down to 3.25% over the first seven years of service.

Schedule of Expected Pension Benefit Payments

Expected future benefits payable by the Company over the next ten years are as follows:

	Amount
2018	$	314,000
2019		313,000
2020		311,000
2021		367,000
2022		711,000
2023-2027		3,813,000

Schedule of Plan's Pension Costs

The SERP’s pension cost included the following components:

	For the Year Ended December 31,
(In thousands)	2017		2016		2015
Service cost – benefits earned during the year	$	143	$	133	$	140
Interest cost on projected benefit obligations		360		367		348
Net amortization and deferral		324		295		654
Net periodic pension cost	$	827	$	795	$	1,142

Schedule of Pretax Amounts in Accumulated Other Comprehensive Loss

The pretax amounts in accumulated other comprehensive loss as of December 31 were as follows:

	The Plan				SERP
(In thousands)	2017		2016		2017		2016
Prior service cost	$	—	$	—	$	—	$	—
Net actuarial loss		23,160		22,237		2,388		2,005
Total	$	23,160	$	22,237	$	2,388	$	2,005

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Restricted Stock Activity

Changes in restricted shares outstanding for the year ended December 31, 2017 were as follows:

			Weighted Average
			Grant Date
	Shares		Fair Value
Balance at December 31, 2016	81,269		$	46.39
Granted	26,064		$	59.46
Vested	(29,167	)	$	47.58
Forfeited	—			—
Balance at December 31, 2017	78,166		$	50.30

Schedule of SARs Activity

Changes in SARs outstanding for the year ended December 31, 2017 were as follows:

	SARs		Weighted Average Exercise Price
Balance at December 31, 2016	261,206		$	34.75
Exercised	(26,970	)		33.09
Forfeited	—			—
Balance at December 31, 2017	234,236			34.97
Exercisable at December 31, 2017	234,236		$	34.97

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

The components of income tax expense (benefit) are as follows:

	For the Years Ended December 31,
(In thousands)	2017			2016		2015
Current:
Federal	$	4,250		$	6,456	$	6,825
State		1,638			941		1,290
Deferred:
Federal		4,256			301		(84	)
State		(259	)		18		(53	)
Total income tax expense	$	9,885		$	7,716	$	7,978

Schedule of Reconciliation of Expected Income Tax Expense (Benefit)

	For the Years Ended December 31,
(In thousands)	2017			2016			2015
Expected income tax expense	$	12,214		$	11,223		$	10,862
(Reductions) increases resulting from:
Tax-exempt income		(3,868	)		(3,754	)		(3,704	)
State taxes, net of federal benefit		896			623			804
Share-based compensation adjustment		(376	)		—			—
Adjustment of deferred tax asset or liability for TCJA		1,824			—			—
Other, net		(805	)		(376	)		16
Total income tax expense	$	9,885		$	7,716		$	7,978

Schedule of Deferred Assets and Liabilities

The tax effects of temporary differences which give rise to significant portions of the deferred tax assets and deferred tax liabilities are presented below:

	December 31,
(In thousands)	2017			2016
Deferred tax assets:
Allowance for loan losses	$	2,413		$	3,718
ASC 715 pension funding liability		6,080			8,969
Net operating loss carryforward⁽¹⁾		76			169
Supplemental executive retirement plan accrual		1,833			2,604
Stock compensation		1,307			1,695
Other		118			177
Total deferred tax assets	$	11,827		$	17,332
Deferred tax liabilities:
Premises and equipment		(2,248	)		(2,731	)
Pension		(1,379	)		(3,601	)
Intangible/assets		(1,091	)		(1,402	)
Unrealized gain on investment in securities available-for-sale		(1,938	)		(560	)
Deferred income		(2,121	)		—
Total deferred tax liabilities	$	(8,777	)	$	(8,294	)
Net deferred tax assets	$	3,050		$	9,038

⁽¹⁾

Schedule of the Reconciliation of Unrecognized Tax Benefits

The reconciliation of the beginning unrecognized tax benefits balance to the ending balance is presented in the following table:

(In thousands)	2017			2016			2015
Balance at January 1	$	1,623		$	1,194		$	1,117
Changes in unrecognized tax benefits as a result of tax positions taken during a prior year		(15	)		407			10
Changes in unrecognized tax benefits as a result of tax position taken during the current year		263			311			277
Decreases in unrecognized tax benefits relating to settlements with taxing authorities		—			—			—
Reductions to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations		(239	)		(289	)		(210	)
Balance at December 31	$	1,632		$	1,623		$	1,194

Disclosures about Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Commitments to Extend Credit, Standby Letters of Credit and Commercial Letters

The following table shows conditional commitments to extend credit, standby letters of credit and commercial letters:

	December 31,
(In thousands)	2017		2016
Conditional commitments to extend credit	$	87,013	$	45,497
Standby letters of credit		14,347		14,381
Commercial letters of credit		3,246		1,962

Schedule of Company's Financial Instruments

Following is a summary of the carrying amounts and fair values of the Company’s financial instruments:

	December 31,
	2017				2016
	Carrying				Carrying
(In thousands)	Amount		Fair Value		Amount		Fair Value
Balance sheet assets:
Cash and cash equivalents	$	228,110	$	228,110	$	266,743	$	266,743
Investment in securities		470,523		470,523		390,552		390,552
Loans, net		676,026		675,020		654,691		652,028
Accrued interest receivable		7,413		7,413		6,543		6,543
Total	$	1,382,072	$	1,381,066	$	1,318,529	$	1,315,866

Balance sheet liabilities:
Deposits	$	678,088	$	678,346	$	621,961	$	622,173
Accounts and drafts payable		661,888		661,888		642,287		642,287
Accrued interest payable		55		55		46		46
Total	$	1,340,031	$	1,340,289	$	1,264,294	$	1,264,506

Industry Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Summary of Segment Information

Summarized information about the Company’s operations in each industry segment for the years ended December 31, 2017, 2016 and 2015, is as follows:

						Corporate,
	Information		Banking			Eliminations
(In thousands)	Services		Services			and Other			Total
*2017*
Fee revenue and other income:
Income from customers	$	93,804	$	1,708		$	—		$	95,512
Intersegment income (expense)		13,317		1,545			(14,862	)		—
Net interest income (expense) after provision for loan losses:
Income from customers		13,400		26,390			—			39,790
Intersegment income (expense)		—		—			—			—
Depreciation and amortization		3,784		150			118			4,052
Income taxes		4,326		5,559			—			9,885
Net income		13,597		11,417			—			25,014
Goodwill		12,433		136			—			12,569
Other intangible assets, net		1,996		—			—			1,996
Total assets	$	800,214	$	830,672		$	(27,677	)	$	1,603,209
*2016*
Fee revenue and other income:
Income from customers	$	84,612	$	1,524		$	—		$	86,136
Intersegment income (expense)		12,164		1,575			(13,739	)		—
Net interest income (expense) after provision for loan losses:
Income from customers		13,820		25,581			—			39,401
Intersegment income (expense)		2		(2	)		—			—
Depreciation and amortization		3,368		165			120			3,653
Income taxes		1,478		6,238			—			7,716
Net income		14,049		10,299			—			24,348
Goodwill		11,454		136			—			11,590
Other intangible assets, net		1,997		—			—			1,997
Total assets	$	763,999	$	756,164		$	(15,324	)	$	1,504,839
*2015*
Fee revenue and other income:
Income from customers	$	82,144	$	1,224		$	—		$	83,368
Intersegment income (expense)		10,078		1,648			(11,726	)		—
Net interest income (expense) after provision for loan losses:
Income from customers		14,598		22,851			—			37,449
Intersegment income (expense)		12		(12	)		—			—
Depreciation and amortization		3,164		151			101			3,416
Income taxes		2,818		5,160			—			7,978
Net income		14,635		8,421			—			23,056
Goodwill		11,454		136			—			11,590
Other intangible assets, net		2,405		—			—			2,405
Total assets	$	702,491	$	761,739		$	(8,724	)	$	1,455,506

Condensed Financial Information of Parent Company (Tables)

12 Months Ended

Dec. 31, 2017

Condensed Financial Information of Parent Company Only Disclosure [Abstract]

Schedule of Condensed Balance Sheet

Following are the condensed balance sheets of the Company (parent company only) and the related condensed statements of income and cash flows.

	Condensed Balance Sheets
	December 31,
(In thousands)	2017		2016
Assets
Cash and due from banks	$	56,462	$	45,464
Short-term investments		48,324		107,898
Securities available-for-sale, at fair value		470,523		390,552
Loans, net		12,239		47,184
Investments in subsidiaries		113,681		101,824
Premises and equipment, net		20,927		20,375
Other assets		199,865		161,317
Total assets	$	922,021	$	874,614
Liabilities and Shareholders’ Equity
Liabilities:
Accounts and drafts payable	$	661,342	$	640,945
Other liabilities		35,533		25,415
Total liabilities		696,875		666,360
Total shareholders’ equity		225,146		208,254
Total liabilities and shareholders’ equity	$	922,021	$	874,614

Schedule of Condensed Statements of Income

	Condensed Statements of Income
	For the Years Ended December 31,
(In thousands)	2017		2016		2015
Income from subsidiaries:
Interest	$	—	$	2	$	12
Management fees		2,172		2,105		2,201
Income from subsidiaries		2,172		2,107		2,213
Information services revenue		93,133		83,543		78,488
Net interest income after provision		13,217		13,389		13,948
Gain on sales of investment securities		—		387		2,910
Other income		483		504		613
Total income		109,005		99,930		98,172
Expenses:
Salaries and employee benefits		70,409		65,968		63,475
Other expenses		20,333		18,133		16,580
Total expenses		90,742		84,101		80,055
Income before income tax and equity in undistributed income of subsidiaries		18,263		15,829		18,117
Income tax expense		4,394		1,540		2,950
Income before undistributed income of subsidiaries		13,869		14,289		15,167
Equity in undistributed income of subsidiaries		11,145		10,059		7,889
Net income	$	25,014	$	24,348	$	23,056

Schedule of Condensed Statements of Cash Flows

	Condensed Statements of Cash Flows
	For the Years Ended December 31,
(In thousands)	2017			2016			2015
Cash flows from operating activities:
Net income	$	25,014		$	24,348		$	23,056
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed income of subsidiaries		(11,145	)		(10,059	)		(7,889	)
Net change in other assets		(41,013	)		(7,085	)		16,100
Net change in other liabilities		10,118			6,683			(2,779	)
Amortization of stock-based awards		1,743			1,677			1,504
Other, net		9,219			7,558			10,389
Net cash (used in) provided by operating activities		(6,064	)		23,122			40,381
Cash flows from investing activities:
Net increase in securities		(80,621	)		(33,025	)		(23,472	)
Net decrease in loans		34,944			40,431			28,343
Purchases of premises and equipment, net		(4,020	)		(4,557	)		(5,708	)
Net cash (used in) provided by investing activities		(49,697	)		2,849			(837	)
Cash flows from financing activities:
Net increase (decrease) in accounts and drafts payable		20,397			64,026			(78,439	)
Cash dividends paid		(10,675	)		(9,979	)		(9,697	)
Purchase of common shares for treasury		(2,270	)		(9,215	)		(10,951	)
Other financing activities		(267	)		1,705			66
Net cash provided by (used in) financing activities		7,185			46,537			(99,021	)
Net increase (decrease) in cash and cash equivalents		(48,576	)		72,508			(59,477	)
Cash and cash equivalents at beginning of year		153,362			80,854			140,331
Cash and cash equivalents at end of year	$	104,786		$	153,362		$	80,854

SUPPLEMENTARY FINANCIAL INFORMATION (Tables)

12 Months Ended

Dec. 31, 2017

Supplemental Income Statement Elements [Abstract]

Schedule of Quarterly Financial Information

	First			Second		Third		Fourth
(In thousands except per share data)	Quarter			Quarter		Quarter		Quarter			YTD
*2017*
Fee revenue and other income	$	22,771		$	23,800	$	24,207	$	24,734		$	95,512
Interest income		9,999			10,332		10,665		10,981			41,977
Interest expense		480			470		571		666			2,187
Net interest income		9,519			9,862		10,094		10,315			39,790
Provision for loan losses		—			—		—		—			—
Operating expense		24,318			24,901		25,042		26,142			100,403
Income tax expense		1,665			2,248		2,396		3,576	*		9,885	*
Net income	$	6,307		$	6,513	$	6,863	$	5,331		$	25,014
Net income per share:
Basic earnings per share	$	.51		$	.53	$	.56	$	.44		$	2.04
Diluted earnings per share		.51			.52		.55		.43			2.01
*2016*
Fee revenue and other income	$	20,505		$	21,457	$	22,149	$	22,025		$	86,136
Interest income		9,777			10,010		9,985		10,158			39,930
Interest expense		513			504		505		507			2,029
Net interest income		9,264			9,506		9,480		9,651			37,901
Provision for loan losses		(1,000	)		—		—		(500	)		(1,500	)
Operating expense		22,916			23,059		23,552		23,946			93,473
Income tax expense		2,020			2,035		1,855		1,806			7,716
Net income	$	5,833		$	5,869	$	6,222	$	6,424		$	24,348
Net income per share:
Basic earnings per share	$	.47		$	.48	$	.51	$	.53		$	1.99
Diluted earnings per share		.47			.47		.50		.52			1.96

⁽¹⁾ Includes one-time, non-cash TCJA charge of $1,824,000

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 15, 2017	Dec. 31, 2017	Feb. 28, 2018	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Percentage holding required to account investments under non-marketable equity investments		20.00%
Percentage of dividend	10.00%
Retained earnings		$ 59,314		$ 118,363
Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Retained earnings			$ 2,286
Building [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives		40 years
Leasehold Improvements [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives		10 years
Software, Equipment, Furniture and Fixtures [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives		7 years
Software, Equipment, Furniture and Fixtures [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives		3 years

Capital Requirements and Regulatory Restrictions (Schedule of Capital Amounts and Ratios) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Cass Information Systems Inc. [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), actual amount	$ 234,389	$ 219,747
Common Equity Tier I Capital (to risk-weighted assets), actual amount	224,184	209,572
Tier I capital (to risk-weighted assets), actual amount	224,184	209,572
Tier I capital (to average assets), actual amount	$ 224,184	$ 209,572
Total capital (to risk-weighted assets), actual ratio	22.53%	22.75%
Common Equity Tier I Capital (to risk-weighted assets), actual ratio	21.55%	21.70%
Tier I capital (to risk-weighted assets), actual ratio	21.55%	21.70%
Tier I capital (to average assets), actual ratio	13.87%	13.83%
Total capital (to risk-weighted assets), capital requirements amount	$ 83,233	$ 77,272
Common Equity Tier I Capital (to risk-weighted assets), capital requirements amount	46,819	43,466
Tier I capital (to risk-weighted assets), capital requirements amount	62,425	57,954
Tier I capital (to average assets), capital requirements amount	$ 64,649	$ 60,620
Total capital (to risk-weighted assets), capital requirements ratio	8.00%	8.00%
Common Equity Tier I Capital (to risk-weighted assets), capital requirements ratio	4.50%	4.50%
Tier I capital (to risk-weighted assets), capital requirements ratio	6.00%	6.00%
Tier I capital (to average assets), capital requirements ratio	4.00%	4.00%
Cass Commercial Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk-weighted assets), actual amount	$ 122,440	$ 110,576
Common Equity Tier I Capital (to risk-weighted assets), actual amount	114,603	102,769
Tier I capital (to risk-weighted assets), actual amount	114,603	102,769
Tier I capital (to average assets), actual amount	$ 114,603	$ 102,769
Total capital (to risk-weighted assets), actual ratio	17.01%	16.72%
Common Equity Tier I Capital (to risk-weighted assets), actual ratio	15.93%	15.54%
Tier I capital (to risk-weighted assets), actual ratio	15.93%	15.54%
Tier I capital (to average assets), actual ratio	14.99%	13.98%
Total capital (to risk-weighted assets), capital requirements amount	$ 57,568	$ 52,898
Common Equity Tier I Capital (to risk-weighted assets), capital requirements amount	32,382	29,755
Tier I capital (to risk-weighted assets), capital requirements amount	43,176	39,674
Tier I capital (to average assets), capital requirements amount	$ 30,581	$ 29,409
Total capital (to risk-weighted assets), capital requirements ratio	8.00%	8.00%
Common Equity Tier I Capital (to risk-weighted assets), capital requirements ratio	4.50%	4.50%
Tier I capital (to risk-weighted assets), capital requirements ratio	6.00%	6.00%
Tier I capital (to average assets), capital requirements ratio	4.00%	4.00%
Total capital (to risk-weighted assets), requirement to be well capitalized amount	$ 71,960	$ 66,123
Common Equity Tier I Capital (to risk-weighted assets), requirement to be well capitalized amount	46,774	42,980
Tier I capital (to risk-weighted assets), requirement to be well capitalized amount	57,568	52,898
Tier I capital (to average assets), requirement to be well capitalized amount	$ 38,227	$ 36,761
Total capital (to risk-weighted assets), requirement to be well capitalized ratio	10.00%	10.00%
Common Equity Tier I Capital (to risk-weighted assets), requirement to be well capitalized ratio	6.50%	6.50%
Tier I capital (to risk-weighted assets), requirement to be well capitalized ratio	8.00%	8.00%
Tier I capital (to average assets), requirement to be well capitalized ratio	5.00%	5.00%

Investment in Securities (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract]
Number of securities that had an unrealized loss	64	108
Number of securities that had an unrealized loss, greater than 12 months	24
Percentage of total securities	17.00%
Premium related to purchase of state and political subdivisions	$ 7,147	$ 5,749
Securities pledged as collateral	3,750	3,750
Proceeds from sales of securities available-for-sale		21,491	$ 99,347
Gross realized gains	0	387	2,910
Gross realized losses	$ 0	$ 0	$ 0

Investment in Securities (Schedule of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Fair Value	$ 470,523	$ 390,552
Gross Unrealized Gains	9,528	5,239
Gross Unrealized Losses	1,383	3,731
Amortized Cost	462,378	389,044
State and Political Subdivisions [Member]
Investment [Line Items]
Fair Value	417,032	370,134
Gross Unrealized Gains	9,528	5,239
Gross Unrealized Losses	661	3,328
Amortized Cost	408,165	368,223
U.S. government agencies [Member]
Investment [Line Items]
Fair Value	45,500	12,672
Gross Unrealized Gains
Gross Unrealized Losses	722	403
Amortized Cost	46,222	13,075
Certificates of Deposit [Member]
Investment [Line Items]
Fair Value	7,991	7,746
Gross Unrealized Gains
Gross Unrealized Losses
Amortized Cost	$ 7,991	$ 7,746

Investment in Securities (Schedule of the Fair Values of Securities with Unrealized Losses) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Estimated fair value less than 12 months	$ 68,938	$ 153,056
Estimated fair value 12 months or more	42,568
Estimated fair value total	111,506	153,056
Unrealized losses, less than 12 months	499	3,731
Unrealized losses, 12 months or more	884
Unrealized losses, total	1,383	3,731
State and Political Subdivisions [Member]
Investment [Line Items]
Estimated fair value less than 12 months	34,755	140,384
Estimated fair value 12 months or more	31,251
Estimated fair value total	66,006	140,384
Unrealized losses, less than 12 months	123	3,328
Unrealized losses, 12 months or more	538
Unrealized losses, total	661	3,328
U.S. government agencies [Member]
Investment [Line Items]
Estimated fair value less than 12 months	34,183	12,672
Estimated fair value 12 months or more	11,317
Estimated fair value total	45,500	12,672
Unrealized losses, less than 12 months	376	403
Unrealized losses, 12 months or more	346
Unrealized losses, total	722	403
Certificates of Deposit [Member]
Investment [Line Items]
Estimated fair value less than 12 months
Estimated fair value 12 months or more
Estimated fair value total
Unrealized losses, less than 12 months
Unrealized losses, 12 months or more
Unrealized losses, total

Investment in Securities (Schedule of Amortized Cost and Fair Value of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Amortized Cost, Due in 1 year or less	$ 22,492
Amortized Cost, Due after 1 year through 5 years	57,922
Amortized Cost, Due after 5 years through 10 years	256,396
Amortized Cost, Due after 10 years	125,568
Amortized Cost, No stated maturity
Amortized Cost, Total	462,378
Fair Value, Due in 1 year or less	22,638
Fair Value, Due after 1 year through 5 years	58,425
Fair Value, Due after 5 years through 10 years	263,961
Fair Value, Due after 10 years	125,499
Fair Value, No stated maturity
Available-for-sale Securities, Total	$ 470,523	$ 390,552

Loans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Loans (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Impaired loans, ALLL	$ 0	$ 0
Nonaccrual loans	0	245
Delinquent loans still accruing interest	0	0
Loans classified as troubled debt restructuring	0	0
Average balance of impaired loans	166	333	$ 3,188
Income recognized on nonaccrual loans under original terms of contract	24	66	390
Income recognized on nonaccrual loans	$ 17	$ 47	$ 34

Loans (Summary of Loan Categories) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 686,231	$ 664,866
Commercial and Industrial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	236,394	214,767
Real Estate Commercial Mortgage [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	94,675	104,779
Real Estate Commercial Construction [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	9,359	6,325
Real Estate Church Related Mortgage [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	316,073	321,168
Real Estate Church Related Construction [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	25,948	11,152
Industrial Revenue Bonds [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	3,374	6,639
Other Loan [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 408	$ 36

Loans (Schedule of the Aging of Loans by Loan Categories) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual		$ 245
Total Loans	$ 686,231	664,866
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual
Total Loans	236,394	214,767
Real Estate Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual		245
Total Loans	94,675	104,779
Real Estate Commercial Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual
Total Loans	9,359	6,325
Real Estate Church Related Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual
Total Loans	316,073	321,168
Real Estate Church Related Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual
Total Loans	25,948	11,152
Industrial Revenue Bonds [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual
Total Loans	3,374	6,639
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non Accrual
Total Loans	408	36
Current [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	686,231	664,609
Current [Member] \| Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	236,394	214,767
Current [Member] \| Real Estate Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	94,675	104,534
Current [Member] \| Real Estate Commercial Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	9,359	6,325
Current [Member] \| Real Estate Church Related Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	316,073	321,168
Current [Member] \| Real Estate Church Related Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	25,948	11,152
Current [Member] \| Industrial Revenue Bonds [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	3,374	6,639
Current [Member] \| Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans	408	24
30-59 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans		12
30-59 Days [Member] \| Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
30-59 Days [Member] \| Real Estate Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
30-59 Days [Member] \| Real Estate Commercial Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
30-59 Days [Member] \| Real Estate Church Related Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
30-59 Days [Member] \| Real Estate Church Related Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
30-59 Days [Member] \| Industrial Revenue Bonds [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
30-59 Days [Member] \| Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans		12
60-89 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Real Estate Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Real Estate Commercial Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Real Estate Church Related Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Real Estate Church Related Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Industrial Revenue Bonds [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
60-89 Days [Member] \| Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Real Estate Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Real Estate Commercial Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Real Estate Church Related Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Real Estate Church Related Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Industrial Revenue Bonds [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans
90 Days and over [Member] \| Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans

Loans (Schedule of the Credit Exposure of the Loan Portfolio) (Details) - USD ($)
$ in Thousands

Dec. 31, 2017

Dec. 31, 2016

Financing Receivable, Recorded Investment [Line Items]

Loans Subject To Normal Monitoring [Member]

$ 686,231

$ 664,866

Financing Receivable, Recorded Investment [Line Items]

Performing Loans Subject To Special Monitoring [Member]

^[1]

683,190

658,984

Financing Receivable, Recorded Investment [Line Items]

Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

3,041

5,637

Financing Receivable, Recorded Investment [Line Items]

Commercial and Industrial [Member]

^[2]

245

Financing Receivable, Recorded Investment [Line Items]

Commercial and Industrial [Member] | Loans Subject To Normal Monitoring [Member]

236,394

214,767

Financing Receivable, Recorded Investment [Line Items]

Commercial and Industrial [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

234,271

213,024

Financing Receivable, Recorded Investment [Line Items]

Commercial and Industrial [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

2,123

1,743

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Mortgage [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Mortgage [Member] | Loans Subject To Normal Monitoring [Member]

94,675

104,779

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Mortgage [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

93,788

103,778

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Mortgage [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

887

756

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Construction [Member]

^[2]

245

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Construction [Member] | Loans Subject To Normal Monitoring [Member]

9,359

6,325

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Construction [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

9,359

6,325

Financing Receivable, Recorded Investment [Line Items]

Real Estate Commercial Construction [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Construction [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Construction [Member] | Loans Subject To Normal Monitoring [Member]

25,948

11,152

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Construction [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

25,948

11,152

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Construction [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Mortgage [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Mortgage [Member] | Loans Subject To Normal Monitoring [Member]

316,073

321,168

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Mortgage [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

316,042

318,030

Financing Receivable, Recorded Investment [Line Items]

Real Estate Church Related Mortgage [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

3,138

Financing Receivable, Recorded Investment [Line Items]

Industrial Revenue Bonds [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Industrial Revenue Bonds [Member] | Loans Subject To Normal Monitoring [Member]

3,374

6,639

Financing Receivable, Recorded Investment [Line Items]

Industrial Revenue Bonds [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

3,374

6,639

Financing Receivable, Recorded Investment [Line Items]

Industrial Revenue Bonds [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

Financing Receivable, Recorded Investment [Line Items]

^[2]

Other [Member]

Other [Member] | Loans Subject To Normal Monitoring [Member]

408

Financing Receivable, Recorded Investment [Line Items]

Other [Member] | Performing Loans Subject To Special Monitoring [Member]

^[1]

408

Financing Receivable, Recorded Investment [Line Items]

Other [Member] | Nonperforming Loans Subject To Special Monitoring [Member]

^[2]

Financing Receivable, Recorded Investment [Line Items]

^[2]

[1]	Loans subject to normal monitoring involve borrowers of acceptable-to-strong credit quality and risk, who have the apparent ability to satisfy their loan obligation.
[2]	Loans subject to special monitoring possess some credit deficiency or potential weakness which requires a high level of management attention.

Loans (Schedule of Recorded Investment and Unpaid Principal for Impaired Loans) (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Financing Receivable, Modifications [Line Items]
Non Accrual	$ 245
Recorded Investment [Member]
Financing Receivable, Modifications [Line Items]
Fair value of impaired loan	245
Upaid Principal Balance [Member]
Financing Receivable, Modifications [Line Items]
Fair value of impaired loan	245
Related Allowance for Loan Losses [Member]
Financing Receivable, Modifications [Line Items]
Fair value of impaired loan
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Commercial and Industrial [Member] \| Recorded Investment [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Commercial and Industrial [Member] \| Upaid Principal Balance [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Commercial and Industrial [Member] \| Related Allowance for Loan Losses [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Real Estate Commercial Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual	245
Real Estate Commercial Mortgage [Member] \| Recorded Investment [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual	245
Real Estate Commercial Mortgage [Member] \| Upaid Principal Balance [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual	245
Real Estate Commercial Mortgage [Member] \| Related Allowance for Loan Losses [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Real Estate Church Related Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Real Estate Church Related Mortgage [Member] \| Recorded Investment [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Real Estate Church Related Mortgage [Member] \| Upaid Principal Balance [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual
Real Estate Church Related Mortgage [Member] \| Related Allowance for Loan Losses [Member]
Financing Receivable, Modifications [Line Items]
Non Accrual

Loans (Summary of Allowance for Loan Losses) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	$ 10,175
Charge-Offs
Recoveries	30
Provision
Allowance for loan losses, Ending Balance	10,205
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	3,261
Charge-Offs
Recoveries	30
Provision	361
Allowance for loan losses, Ending Balance	3,652
Real Estate Commercial Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	1,662
Charge-Offs
Recoveries
Provision	(268)
Allowance for loan losses, Ending Balance	1,394
Real Estate Commercial Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	47
Charge-Offs
Recoveries
Provision	23
Allowance for loan losses, Ending Balance	70
Real Estate Church Related Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	4,027
Charge-Offs
Recoveries
Provision	(65)
Allowance for loan losses, Ending Balance	3,962
Real Estate Church Related Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	85
Charge-Offs
Recoveries
Provision	111
Allowance for loan losses, Ending Balance	196
Industrial Revenue Bonds [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	101
Charge-Offs
Recoveries
Provision	(49)
Allowance for loan losses, Ending Balance	52
Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses, Beginning Balance	992
Charge-Offs
Recoveries
Provision	(113)
Allowance for loan losses, Ending Balance	$ 879

Premises and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 3,627	$ 3,245	$ 3,008
Rent expense	$ 1,499	$ 1,397	$ 1,387

Premises and Equipment (Summary of Premises and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 52,484	$ 48,387
Less accumulated depreciation	30,898	27,301
Total	21,586	21,086
Land [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	873	873
Building [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	13,386	13,087
Leaseholds and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	2,120	2,098
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	14,801	13,248
Software [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	4,819	4,704
Internally Developed Software [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 16,485	$ 14,377

Premises and Equipment (Schedule of Future Minimum Rental Payments) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Abstract]
2018	$ 1,518
2019	1,270
2020	1,245
2021	1,118
2022	1,086
2023	226
Total	$ 6,463

Acquired Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 427	$ 408	$ 408
2018	442
2019	412
2020	406
2021	406
2022	88
Recorded intangible assets	1,405
Customer Lists [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Recorded intangible assets	$ 355
Customer Lists [Member] \| Minimum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	7 years
Customer Lists [Member] \| Maximum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	10 years
Patents [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	18 years
Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Recorded intangible assets	$ 71
Noncompete Agreements [Member] \| Minimum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	2 years
Noncompete Agreements [Member] \| Maximum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	5 years
Software [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	3 years
Other Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	15 years
Goodwill [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Recorded intangible assets	$ 979

Acquired Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($)
$ in Thousands

Dec. 31, 2017

Dec. 31, 2016

$ 18,222

$ 16,817

Goodwill, Gross Carrying Amount

(3,657)

(3,230)

Unamortized intangible assets:

^[1]

12,796

11,817

Goodwill, Accumulated Amortization

^[1]

(227)

Customer Lists [Member]

4,288

3,933

(2,702)

(2,342)

Patents [Member]

Noncompete Agreements [Member]

(12)

(8)

332

261

(291)

(261)

Software [Member]

234

Other Intangible Assets [Member]

(234)

500

Defined Benefit Plan Disclosure [Line Items]

$ (191)

$ (158)

[1]	Amortization through December 31, 2001 prior to adoption of FASB ASC 350.

Interest-Bearing Deposits (Schedule of Interest-bearing Deposits) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest-Bearing Deposits [Abstract]
Interest-bearing demand deposits	$ 332,881	$ 322,091
Savings deposits	11,168	29,430
Time deposits:
Less than $100	2,658	3,523
$100 to less than $250	33,385	37,179
$250 or more	16,455	15,082
Total	$ 396,547	$ 407,305
Weighted average interest rate	0.56%	0.48%

Interest-Bearing Deposits (Schedule of Interest on Deposits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest-Bearing Deposits [Abstract]
Interest-bearing demand deposits	$ 1,611	$ 1,387	$ 1,392
Savings deposits	79	100	65
Time deposits:
Less than $100	234	274	346
$100 to less than $250	114	191	119
$250 or more	149	77	189
Total	$ 2,187	$ 2,029	$ 2,111

Interest-Bearing Deposits (Schedule of Maturities of Time Deposits) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Due within:
One year	$ 48,370	$ 48,740
Two years	281	4,752
Three years	2,383	155
Four years	25	2,072
Five years	1,439	65
Total	$ 52,498	$ 55,784
Percent of Total One year	92.10%	87.40%
Percent of Total Two years	0.50%	8.50%
Percent of Total Three years	4.50%	0.30%
Percent of Total Four years	0.10%	3.70%
Percent of Total Five years	2.80%	0.10%
Total	100.00%	100.00%

Unused Available Lines of Credit (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Unsecured Debt [Member]
Line of Credit Facility [Line Items]
Line of credit amount	$ 68,000
Unsecured Debt [Member] \| US Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	20,000
Unsecured Debt [Member] \| Wells Fargo Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	15,000
Unsecured Debt [Member] \| PNC Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	12,000
Unsecured Debt [Member] \| Frost National Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	10,000
Unsecured Debt [Member] \| JPM Chase Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	6,000
Unsecured Debt [Member] \| UMB Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	5,000
Secured Debt [Member] \| UMB Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	50,000
Secured Debt [Member] \| Federal Home Loan Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	204,789
Secured Debt [Member] \| First Tennessee Bank [Member]
Line of Credit Facility [Line Items]
Line of credit amount	$ 50,000

Common Stock and Earnings per Share (Schedule of Common Stock Outstanding) (Details)	12 Months Ended
	Dec. 31, 2017 shares
Earnings Per Share [Abstract]
Shares outstanding at January 1	11,188,466
10% stock dividend issued December 15, 2017	1,116,711
Issuance of common stock:
Employee restricted stock grants	3,825
Employee SARs exercised	7,547
Directors' compensation	8,389
Shares repurchased	(38,042)
Shares outstanding at December 31	12,286,896

Common Stock and Earnings per Share (Schedule of Calculations of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic
Net income	$ 5,331	$ 6,863	$ 6,513	$ 6,307	$ 6,424	$ 6,222	$ 5,869	$ 5,833	$ 25,014	$ 24,348	$ 23,056
Weighted average common shares outstanding (in shares)									12,250,465	12,265,434	12,494,466
Basic earnings per share (in dollars per share)	$ 0.44	$ 0.56	$ 0.53	$ 0.51	$ .53	$ .51	$ .48	$ .47	$ 2.04	$ 1.99	$ 1.85
Diluted
Net income	$ 5,331	$ 6,863	$ 6,513	$ 6,307	$ 6,424	$ 6,222	$ 5,869	$ 5,833	$ 25,014	$ 24,348	$ 23,056
Weighted average common shares outstanding (in shares)									12,250,465	12,265,434	12,494,466
Effect of dilutive restricted stock, PBRS and SARs (in shares)									179,445	172,386	175,784
Weighted average common shares outstanding assuming dilution (in shares)									12,429,910	12,437,820	12,670,250
Diluted earnings per share (in dollars per share)	$ 0.43	$ 0.55	$ 0.52	$ 0.51	$ .52	$ .50	$ .47	$ .47	$ 2.01	$ 1.96	$ 1.82

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	$ 2,031	$ 1,885
Defined contribution plan, contribution amount	925	658	$ 623
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	85,236	74,425
Recognized prior service (cost) benefit	0
Net gains (losses) as a component of net periodic benefit cost	1,409
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	8,734	7,904
Contributions for plan	5,799	5,367	5,211
Benefits paid	247	$ 247	$ 243
Recognized prior service (cost) benefit	0
Net gains (losses) as a component of net periodic benefit cost	$ 582
Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset	51.00%
U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset	25.00%
Non-U.S. Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset	30.00%

Employee Benefit Plans (Schedule of Projected Benefit Obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Projected benefit obligation:
Balance, January 1	$ 85,551	$ 78,369
Service cost	3,733	3,559
Interest cost	3,621	3,505
Actuarial (gain) loss	7,916	2,003
Benefits paid	(2,031)	(1,885)
Balance, December 31	98,790	85,551
Plan assets:
Fair value, January 1	73,168	71,174
Actual return	10,290	3,879
Employer contribution
Benefits paid	(2,031)	(1,885)
Fair value, December 31	81,427	73,168
Funded status:
Accrued pension liability	$ (17,363)	$ (12,383)

Employee Benefit Plans (Schedule of Assumptions used to Determine the Projected Benefit Obligation) (Details) - Defined Benefit Plan [Member]

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Weighted average discount rate

3.75%

4.25%

4.50%

Rate of increase in compensation levels

^[1]

[1]	6.0% graded down to 3.25% over the first seven years of service

Employee Benefit Plans (Schedule of Expected Pension Benefit Payments) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Retirement Benefits [Abstract]
2018	$ 2,679
2019	2,823
2020	3,045
2021	3,300
2022	3,693
2023-2027	$ 23,682

Employee Benefit Plans (Schedule of Plan's Pension Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 3,733	$ 3,559
Interest cost on projected benefit obligations	3,621	3,505
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	3,733	3,559	$ 3,796
Interest cost on projected benefit obligations	3,621	3,505	3,178
Expected return on plan assets	(4,681)	(4,734)	(4,864)
Net amortization and deferral	1,382	1,259	1,542
Net periodic pension cost	$ 4,055	$ 3,589	$ 3,652

Employee Benefit Plans (Schedule of Assumptions used to Determine Net Pension Cost) (Details)

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Retirement Benefits [Abstract]

Weighted average discount rate

4.25%

4.50%

4.00%

Rate of increase in compensation levels

^[1]

Expected long-term rate of return on assets

6.50%

6.75%

[1]	6.0% graded down to 3.25% over the first seven years of service

Employee Benefit Plans (Schedule of Long-term Rate of Return on Assets (Details)	12 Months Ended
	Dec. 31, 2017
Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of Total Portfolio	51.00%
One-Year Nominal Return	4.55%
Annual Standard Deviation	4.55%
Large Cap U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of Total Portfolio	14.00%
One-Year Nominal Return	7.00%
Annual Standard Deviation	15.85%
Small Cap U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of Total Portfolio	5.00%
One-Year Nominal Return	8.10%
Annual Standard Deviation	19.70%
International (Developed) [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of Total Portfolio	25.00%
One-Year Nominal Return	7.99%
Annual Standard Deviation	17.93%
International (Emerging) [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent of Total Portfolio	5.00%
One-Year Nominal Return	10.56%
Annual Standard Deviation	27.35%

Employee Benefit Plans (Summary of the Fair Value Measurements by Type of Asset) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Total	$ 81,427	$ 73,168	$ 71,174
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	374	340
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	81,053	72,828
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	374	340
Cash [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	374	340
Cash [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		13,306
U.S. Large Cap Growth [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Large Cap Growth [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		13,306
U.S. Small/Mid Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,111	5,655
U.S. Small/Mid Cap Growth [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Small/Mid Cap Growth [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,111	5,655
Non-U.S. Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	21,065	10,558
Non-U.S. Core [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
Non-U.S. Core [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	21,065	10,558
U.S. Large Cap Passive [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,717	7,364
U.S. Large Cap Passive [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Large Cap Passive [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,717	7,364
Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,052	652
Emerging Markets [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
Emerging Markets [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,052	652
U.S. Core Opportunistic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,284	24,438
U.S. Core Opportunistic [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Core Opportunistic [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,284	24,438
U.S. Passive [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	24,345	9,571
U.S. Passive [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Passive [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	24,345	9,571
Opportunistic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,479	1,254
Opportunistic [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
Opportunistic [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 4,479	$ 1,254

Employee Benefit Plans (Summary of the Activity in the SERP's Projected Benefit Obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefit obligation:
Balance, January 1	$ 85,551	$ 78,369
Service cost	3,733	3,559
Interest cost	3,621	3,505
Benefits paid	(2,031)	(1,885)
Actuarial (gain) loss	7,916	2,003
Balance, December 31	98,790	85,551	$ 78,369
Supplemental Executive Retirement Plan [Member]
Benefit obligation:
Balance, January 1	9,132	8,748
Service cost	143	133	140
Interest cost	360	367	348
Benefits paid	(247)	(247)	(243)
Actuarial (gain) loss	706	131
Balance, December 31	$ 10,094	$ 9,132	$ 8,748

Employee Benefit Plans (Schedule of Assumptions used to Determine Projected Benefit Obligation of the SERP) (Details) - Supplemental Executive Retirement Plan [Member]

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Defined Benefit Plan Disclosure [Line Items]

Weighted average discount rate

3.50%

4.00%

4.25%

Rate of increase in compensation levels

^[1]

[1]	6.0% graded down to 3.25% over the first seven years of service

Employee Benefit Plans (Schedule of Expected Future Benefits Payable) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
2018	$ 2,679
2019	2,823
2020	3,045
2021	3,300
2022	3,693
2023-2027	23,682
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	314
2019	313
2020	311
2021	367
2022	711
2023-2027	$ 3,813

Employee Benefit Plans (Schedule of SERP's Pension Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$ 3,733	$ 3,559
Interest cost on projected benefit obligations	3,621	3,505
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	143	133	$ 140
Interest cost on projected benefit obligations	360	367	348
Net amortization and deferral	324	295	654
Net periodic pension cost	$ 827	$ 795	$ 1,142

Employee Benefit Plans (Schedule of the Pretax amounts in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost
Net actuarial loss	23,160	22,237
Total	23,160	22,237
Supplemental Executive Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost
Net actuarial loss	2,388	2,005
Total	$ 2,388	$ 2,005

Stock-based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 15, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance		1,500,000
Percentage of dividend	10.00%
Share-Based Compensation		$ 2,339	$ 1,959	$ 2,059
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted		26,064	39,816	47,065
Shares granted, weighted average grant date market value			$ 45.75	$ 46.40
Vesting period		3 years	3 years
Amortization of restricted stock bonus		$ 1,743	$ 1,712	$ 1,514
Total unrecognized compensation expense		$ 1,345
Total unrecognized compensation expense, weighted average period		7 months 17 days
Total fair value of shares vested		$ 1,550	1,500	$ 1,089
Fair value of granted shares per share		$ 59.46
Performance-based restricted shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted		25,342
Vesting period		3 years
Fair value of granted shares per share		$ 59.20
Expense incurred to grant shares		$ 579
Percentage of financial goal		124.00%
Performance-based restricted shares [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest		0.00%
Performance-based restricted shares [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target opportunity for awards to vest		150.00%
SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense		$ 0
Total intrinsic value of options exercised		$ 892	$ 2,162
Average remaining contractual term		5 years 11 days	5 years 2 months 19 days
Outstanding, Aggregate Intrinsic Value		$ 7,291	$ 8,395
Share-Based Compensation		$ 18

Stock-based Compensation (Schedule of Restricted Stock Outstanding) (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
Balance at December 31, 2016	81,269
Granted	26,064	39,816	47,065
Vested	(29,167)
Forfeited
Balance at December 31, 2017	78,166	81,269
Weighted Average Grant Date Fair Value
Balance at December 31, 2016	$ 46.39
Granted	59.46
Vested	47.58
Forfeited
Balance at December 31, 2017	$ 50.30	$ 46.39

Stock-based Compensation (Schedule of SARs Oustanding) (Details) - SARs [Member]	12 Months Ended
	Dec. 31, 2017 $ / shares shares
SARs
Balance at December 31, 2016 \| shares	261,206
Exercised \| shares	(26,970)
Forfeited \| shares
Balance at December 31, 2017 \| shares	234,236
Exercisable at December 31, 2017 \| shares	234,236
Weighted Average Exercise Price
Balance at December 31, 2016 \| $ / shares	$ 34.75
Exercised \| $ / shares	33.09
Forfeited \| $ / shares
Balance at December 31, 2017 \| $ / shares	34.97
Exercisable at December 31, 2017 \| $ / shares	$ 34.97

Other Operating Expense (Schedule of Other Operating Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Postage and supplies	$ 2,087	$ 1,925	$ 1,954
Promotional expense	2,557	2,187	2,268
Professional fees	1,650	1,930	1,690
Outside service fees	4,424	3,316	2,848
Data processing services	897	372	357
Telecommunications	749	1,000	1,068
Other	1,722	1,913	1,185
Total other operating expense	$ 14,086	$ 12,643	$ 11,370

Income Taxes (Narrative) (Details) - USD ($)
$ in Thousands

1 Months Ended

3 Months Ended

12 Months Ended

Jan. 31, 2018

Dec. 22, 2017

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Statutory federal tax rate

35.00%

Change in corporate federal statutory income tax rate

21.00%

Net operating loss carryforward

^[1]

$ 76

$ 169

$ 76

$ 169

Amounts of tax benefits that would affect effective tax rate if recognized

1,464

1,225

1,464

1,225

$ 861

Income tax accrued interest

139

108

139

108

Increase (reduction) in accrued interest

Reduction of tax benefits over the next twelve months

299

Percentage of pre-tax income tax rate

3,576

^[2]

$ 2,396

$ 2,248

$ 1,665

$ 1,806

$ 1,855

$ 2,035

$ 2,020

$ 9,885

^[2]

$ 7,716

$ 7,978

28.00%

24.00%

26.00%

Non-cash charge

$ 1,824

Deferred tax inventory net credit amount

462

Change in AOCI related to pension and unrealized gains/losses on securities available for sale

$ 2,286

Subsequent Event [Member]

Change in corporate federal statutory income tax rate

25.00%

Minimum [Member]

Percentage of one time charge

28.00%

Maximum [Member]

Percentage of one time charge

25.00%

Franklin Bancorp [Member]

Net operating loss carryforward

361

$ 361

Limitations on use

$ 122

Net operating loss carryforward expiration date

Dec. 31, 2020

[1]	As of December 31, 2017, the Company had approximately $361,000 of net operating loss carry forwards as a result of the acquisition of Franklin Bancorp. The utilization of the net operating loss carry forward is subject to Section 382 of the Internal Revenue Code and limits the Company's use to approximately $122,000 per year during the carry forward period, which expires in 2020.
[2]	Includes one-time, non-cash TCJA charge of $1,824,000

Income Taxes (Components of Income Tax Expense (Benefit)) (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

^[1]

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Current:

Federal

$ 4,250

$ 6,456

$ 6,825

State

1,638

941

1,290

Deferred:

Federal

4,256

301

(84)

State

(259)

(53)

Total income tax expense

$ 3,576

$ 2,396

$ 2,248

$ 1,665

$ 1,806

$ 1,855

$ 2,035

$ 2,020

$ 9,885

^[1]

$ 7,716

$ 7,978

[1]	Includes one-time, non-cash TCJA charge of $1,824,000

Income Taxes (Schedule of Reconciliation of Expected Income Tax Expense (Benefit)) (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

^[1]

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Expected income tax expense

$ 12,214

$ 11,223

$ 10,862

(Reductions) increases resulting from:

Tax-exempt income

(3,868)

(3,754)

(3,704)

State taxes, net of federal benefit

896

623

804

Share-based compensation adjustment

(376)

Adjustment of deferred tax asset or liability for TCJA

1,824

Other, net

(805)

(376)

Total income tax expense

$ 3,576

$ 2,396

$ 2,248

$ 1,665

$ 1,806

$ 1,855

$ 2,035

$ 2,020

$ 9,885

^[1]

$ 7,716

$ 7,978

[1]	Includes one-time, non-cash TCJA charge of $1,824,000

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($)
$ in Thousands

Dec. 31, 2017

Dec. 31, 2016

Deferred tax assets:

Allowance for loan losses

$ 2,413

$ 3,718

ASC 715 pension funding liability

6,080

8,969

Net operating loss carryforward

^[1]

169

Supplemental executive retirement plan accrual

1,833

2,604

Stock compensation

1,307

1,695

Other

118

177

Total deferred tax assets

11,827

17,332

Deferred tax liabilities:

Premises and equipment

(2,248)

(2,731)

Pension

(1,379)

(3,601)

Intangible/assets

(1,091)

(1,402)

Unrealized gain on investment in securities available-for-sale

(1,938)

(560)

Deferred income

(2,121)

Total deferred tax liabilities

(8,777)

(8,294)

Net deferred tax assets

$ 3,050

$ 9,038

[1]

As of December 31, 2017, the Company had approximately $361,000 of net operating loss carry forwards as a result of the acquisition of Franklin Bancorp. The utilization of the net operating loss carry forward is subject to Section 382 of the Internal Revenue Code and limits the Company's use to approximately $122,000 per year during the carry forward period, which expires in 2020.

Income Taxes (Schedule of the Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at January 1	$ 1,623	$ 1,194	$ 1,117
Changes in unrecognized tax benefits as a result of tax positions taken during a prior year	(15)	407	10
Changes in unrecognized tax benefits as a result of tax position taken during the current year	263	311	277
Decreases in unrecognized tax benefits relating to settlements with taxing authorities
Reductions to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations	(239)	(289)	(210)
Balance at December 31	$ 1,632	$ 1,623	$ 1,194

Disclosures about Fair Value of Financial Instruments (Schedule of Commitments to Extend Credit, Standby Letters of Credit and Commercial Letters) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitments To Extend Credit [Member]
Other Commitments [Line Items]
Long-term Line of Credit	$ 87,013	$ 45,497
Standby Letters Of Credit [Member]
Other Commitments [Line Items]
Long-term Line of Credit	14,347	14,381
Commercial Letters Of Credit [Member]
Other Commitments [Line Items]
Long-term Line of Credit	$ 3,246	$ 1,962

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

Disclosures about Fair Value of Financial Instruments (Summary of the Company's Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Cash and cash equivalents, Carrying Amount	$ 228,110	$ 266,743	$ 253,172	$ 294,335
Investment in securities, Carrying Amount	470,523	390,552
Loans, net, Carrying Amount	676,026	654,691
Accrued interest receivable, Carrying Amount	7,413	6,543
Assets, Carrying Amount	1,382,072	1,318,529
Cash and cash equivalents, Fair Value	228,110	266,743
Investment in securities, Fair Value	470,523	390,552
Loans, net, Fair Value	675,020	652,028
Accrued interest receivable, Fair Value	7,413	6,543
Assets, Fair Value	1,381,066	1,315,866
Deposits, Carrying Amount	678,088	621,961
Accounts and drafts payable, Carrying Amount	661,888	642,287
Accrued interest payable, Carrying Amount	55	46
Liabilities, Carrying Amount	1,340,031	1,264,294
Deposits, Fair Value	678,346	622,173
Accounts and drafts payable, Fair Value	661,888	642,287
Accrued interest payable, Fair Value	55	46
Liabilities, Fair Value	$ 1,340,289	$ 1,264,506

Industry Segment Information (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

$ 95,512

$ 86,136

$ 83,368

Net interest income (expense) after provision for loan losses:

39,790

39,401

37,449

4,052

3,653

3,416

$ 3,576

^[1]

$ 2,396

$ 2,248

$ 1,665

$ 1,806

$ 1,855

$ 2,035

$ 2,020

9,885

^[1]

7,716

7,978

5,331

$ 6,863

$ 6,513

$ 6,307

6,424

$ 6,222

$ 5,869

$ 5,833

25,014

24,348

23,056

12,569

11,590

12,569

11,590

1,996

1,997

1,996

1,997

2,405

Information Services [Member]

1,603,209

1,504,839

1,603,209

1,504,839

1,455,506

93,804

84,612

82,144

Net interest income (expense) after provision for loan losses:

13,317

12,164

10,078

13,400

13,820

14,598

3,784

3,368

3,164

4,326

1,478

2,818

13,597

14,049

14,635

12,433

11,454

12,433

11,454

1,996

1,997

1,996

1,997

2,405

Banking Services [Member]

800,214

763,999

800,214

763,999

702,491

1,708

1,524

1,224

Net interest income (expense) after provision for loan losses:

1,545

1,575

1,648

26,390

25,581

22,851

(2)

(12)

150

165

151

5,559

6,238

5,160

11,417

10,299

8,421

136

Corporate Eliminations and Other [Member]

830,672

756,164

830,672

756,164

761,739

Net interest income (expense) after provision for loan losses:

(14,862)

(13,739)

(11,726)

118

120

101

Net interest income after provision

$ (27,677)

$ (15,324)

$ (27,677)

$ (15,324)

$ (8,724)

[1]	Includes one-time, non-cash TCJA charge of $1,824,000

Condensed Financial Information of Parent Company (Schedule of Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and due from banks	$ 17,422	$ 11,814
Securities available-for-sale, at fair value	470,523	390,552
Loans, net	676,026	654,691
Premises and equipment, net	21,586	21,086
Other assets	36,369	36,388
Total assets	1,603,209	1,504,839	$ 1,455,506
Liabilities and Shareholders' Equity
Accounts and drafts payable	661,888	642,287
Other liabilities	38,145	32,556
Total liabilities	1,378,121	1,296,804
Total shareholders' equity	225,088	208,035	$ 207,378	$ 200,432
Total liabilities and shareholders' equity	1,603,209	1,504,839
Parent [Member]
Assets
Cash and due from banks	56,462	45,464
Short-term investments	48,324	107,898
Securities available-for-sale, at fair value	470,523	390,552
Loans, net	12,239	47,184
Investments in subsidiaries	113,681	101,824
Premises and equipment, net	20,927	20,375
Other assets	199,865	161,317
Total assets	922,021	874,614
Liabilities and Shareholders' Equity
Accounts and drafts payable	661,342	640,945
Other liabilities	35,533	25,415
Total liabilities	696,875	666,360
Total shareholders' equity	225,146	208,254
Total liabilities and shareholders' equity	$ 922,021	$ 874,614

Condensed Financial Information of Parent Company (Schedule of Condensed Statement of Income) (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Income from subsidiaries:

$ 39,790

$ 39,401

$ 37,449

Gain on sales of investment securities

387

2,910

Total net revenue

135,302

125,537

120,817

Expenses:

Salaries and employee benefits

77,339

72,581

70,314

Other expenses

1,722

1,913

1,185

Total operating expense

$ 26,142

$ 25,042

$ 24,901

$ 24,318

$ 23,946

$ 23,552

$ 23,059

$ 22,916

100,403

93,473

89,783

3,576

^[1]

2,396

2,248

1,665

1,806

1,855

2,035

2,020

9,885

^[1]

7,716

7,978

Information services revenue

$ 5,331

$ 6,863

$ 6,513

$ 6,307

$ 6,424

$ 6,222

$ 5,869

$ 5,833

25,014

24,348

23,056

Parent Company [Member]

Income from subsidiaries:

Interest

Management fees

2,172

2,105

2,201

Income from subsidiaries

2,172

2,107

2,213

93,133

83,543

78,488

Net interest income after provision

13,217

13,389

13,948

Gain on sales of investment securities

387

2,910

Other income

483

504

613

Total net revenue

109,005

99,930

98,172

Expenses:

Salaries and employee benefits

70,409

65,968

63,475

Other expenses

20,333

18,133

16,580

Total operating expense

90,742

84,101

80,055

Income before income tax and equity in undistributed income of subsidiaries

18,263

15,829

18,117

Income before undistributed income of subsidiaries

4,394

1,540

2,950

13,869

14,289

15,167

Equity in undistributed income of subsidiaries

11,145

10,059

7,889

Supplemental Income Statement Elements [Abstract]

$ 25,014

$ 24,348

$ 23,056

[1]	Includes one-time, non-cash TCJA charge of $1,824,000

Condensed Financial Information of Parent Company (Schedule of Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 5,331	$ 6,863	$ 6,513	$ 6,307	$ 6,424	$ 6,222	$ 5,869	$ 5,833	$ 25,014	$ 24,348	$ 23,056
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net cash (used in) provided by operating activities									38,890	35,189	33,493
Cash flows from investing activities:
Net increase in securities									(124,777)	(96,290)	(161,279)
Net decrease in loans									(21,335)	(5,771)	10,882
Purchases of premises and equipment, net									(4,127)	(4,684)	(5,747)
Net cash (used in) provided by investing activities									(139,839)	(41,551)	(3,636)
Cash flows from financing activities:
Net increase (decrease) in accounts and drafts payable									19,601	65,028	(78,169)
Cash dividends paid									(10,675)	(9,979)	(9,697)
Purchase of common shares of treasury									(2,270)	(9,215)	(10,951)
Other financing activities									(467)	(1,378)	(488)
Net cash provided by (used in) financing activities									62,316	19,933	(71,020)
Net increase (decrease) in cash and cash equivalents									(38,633)	13,571	(41,163)
Cash and cash equivalents at beginning of year				266,743				253,172	266,743	253,172	294,335
Cash and cash equivalents at end of year	228,110				266,743				228,110	266,743	253,172
Parent Company [Member]
Cash flows from operating activities:
Net income									25,014	24,348	23,056
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed income of subsidiaries									(11,145)	(10,059)	(7,889)
Net change in other assets									(41,013)	(7,085)	16,100
Net change in other liabilities									10,118	6,683	(2,779)
Amortization of stock-based awards									1,743	1,677	1,504
Other, net									9,219	7,558	10,389
Net cash (used in) provided by operating activities									(6,064)	23,122	40,381
Cash flows from investing activities:
Net increase in securities									(80,621)	(33,025)	(23,472)
Net decrease in loans									34,944	40,431	28,343
Purchases of premises and equipment, net									(4,020)	(4,557)	(5,708)
Net cash (used in) provided by investing activities									(49,697)	2,849	(837)
Cash flows from financing activities:
Net increase (decrease) in accounts and drafts payable									20,397	64,026	(78,439)
Cash dividends paid									(10,675)	(9,979)	(9,697)
Purchase of common shares of treasury									(2,270)	(9,215)	(10,951)
Other financing activities									(267)	1,705	66
Net cash provided by (used in) financing activities									7,185	46,537	(99,021)
Net increase (decrease) in cash and cash equivalents									(48,576)	72,508	(59,477)
Cash and cash equivalents at beginning of year				$ 153,362				$ 80,854	153,362	80,854	140,331
Cash and cash equivalents at end of year	$ 104,786				$ 153,362				$ 104,786	$ 153,362	$ 80,854

SUPPLEMENTARY FINANCIAL INFORMATION (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Fee revenue and other income

$ 24,734

$ 24,207

$ 23,800

$ 22,771

$ 22,025

$ 22,149

$ 21,457

$ 20,505

$ 95,512

$ 86,136

$ 83,368

Interest income

10,981

10,665

10,332

9,999

10,158

9,985

10,010

9,777

41,977

39,930

38,710

Interest expense

666

571

470

480

507

505

504

513

2,187

2,029

2,111

Net interest income

10,315

10,094

9,862

9,519

9,651

9,480

9,506

9,264

39,790

37,901

36,599

Provision for loan losses

(500)

(1,000)

(1,500)

(850)

Operating expense

26,142

25,042

24,901

24,318

23,946

23,552

23,059

22,916

100,403

93,473

89,783

3,576

^[1]

2,396

2,248

1,665

1,806

1,855

2,035

2,020

9,885

^[1]

7,716

7,978