REGULATORY CAPITAL AND OTHER REGULATORY MATTERS (Schedule of Regulatory Capital) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
First Banks, Inc. (Consolidated) [Member]
Total capital (to risk-weighted assets):
Total Capital	$ 475,312		$ 405,856
Total Capital to Risk-Weighted Assets	12.25%		11.13%
Total Capital Required for Capital Adequacy	8.00%
Tier 1 capital (to risk-weighted assets):
Tier 1 capital	284,396		239,868
Total Capital to Risk-Weighted Assets	7.33%		6.58%
Total Capital Required for Capital Adequacy	4.00%
Tier 1 capital (to average assets):
Tier 1 capital	284,396		239,868
Total Capital to Risk-Weighted Assets	5.01%		4.12%
Total Capital Required for Capital Adequacy	4.00%
First Bank [Member]
Total capital (to risk-weighted assets):
Total Capital	691,350		734,535
Total Capital to Risk-Weighted Assets	17.81%	[1]	20.12%
Total Capital Required for Capital Adequacy	8.00%
Total Capital Required to be Well Capitalized	10.00%
Tier 1 capital (to risk-weighted assets):
Tier 1 capital	642,593		688,427
Total Capital to Risk-Weighted Assets	16.55%	[1]	18.86%
Total Capital Required for Capital Adequacy	4.00%
Total Capital Required to be Well Capitalized	6.00%
Tier 1 capital (to average assets):
Tier 1 capital	$ 642,593		$ 688,427
Total Capital to Risk-Weighted Assets	11.35%	[1]	11.77%
Total Capital Required for Capital Adequacy	4.00%
Total Capital Required to be Well Capitalized	5.00%

[1] The reduction in First Bank's regulatory capital ratios during 2014 primarily resulted from the payment of $95.0 million of dividends to the Company in 2014.