Capital Requirements and Regulatory Restrictions (Tables)

12 Months Ended

Dec. 31, 2016

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, 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
At December 31, 2015
Total capital (to risk-weighted assets)
Cass Information Systems, Inc.	$	212,717	23.31	%	$	72,994	8.00	%	$	N/A	N/A %
Cass Commercial Bank		99,872	16.90			47,281	8.00			59,102	10.00
Common Equity Tier I Capital (to risk-
weighted assets)
Cass Information Systems, Inc.		201,312	22.06			41,059	4.50			N/A	N/A
Cass Commercial Bank		92,470	15.65			26,596	4.50			38,416	6.50
Tier I capital (to risk-weighted assets)
Cass Information Systems, Inc.		201,312	22.06			54,746	6.00			N/A	N/A
Cass Commercial Bank		92,470	15.65			35,461	6.00			47,281	8.00
Tier I capital (to average assets)
Cass Information Systems, Inc.		201,312	13.88			57,995	4.00			N/A	N/A
Cass Commercial Bank		92,470	13.15			28,124	4.00			35,155	5.00