Capital Requirements and Regulatory Restrictions (Tables)

12 Months Ended

Dec. 31, 2012

Banking and Thrift [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]

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

					Capital				Requirement to be
	Actual				Requirements				Well Capitalized
(In thousands)	Amount		Ratio		Amount		Ratio		Amount		Ratio
At December 31, 2012
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	175,802	19.87	%	$	70,767	8.00	%	$	N/A	N/A	%
Cass Commercial Bank		75,300	13.41			44,909	8.00			56,136	10.00
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		164,729	18.62			35,384	4.00			N/A	N/A
Cass Commercial Bank		68,261	12.16			22,454	4.00			33,682	6.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		164,729	12.26			40,294	3.00			N/A	N/A
Cass Commercial Bank		68,261	10.64			19,238	3.00			32,063	5.00
At December 31, 2011
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	166,605	19.03	%	$	70,033	8.00	%	$	N/A	N/A	%
Cass Commercial Bank		66,851	12.71			42,070	8.00			52,588	10.00
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		155,638	17.78			35,016	4.00			N/A	N/A
Cass Commercial Bank		60,248	11.46			21,035	4.00			31,553	6.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		155,638	11.53			40,502	3.00			N/A	N/A
Cass Commercial Bank		60,248	9.49			19,044	3.00			31,741	5.00