v2.4.0.6
Document And Entity Information (USD $)
12 Months Ended
Dec. 31, 2011
Mar. 05, 2012
Jun. 30, 2011
Entity Registrant Name CASS INFORMATION SYSTEMS INC    
Entity Central Index Key 0000708781    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Trading Symbol cass    
Entity Common Stock, Shares Outstanding   10,383,118  
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2011    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2011    
Entity Well-Known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Public Float     $ 327,184,000