PARENT COMPANY ONLY FINANCIAL INFORMATION (Condensed Statements of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income attributable to First Banks, Inc.	$ 21,655	$ 241,744	$ 26,278
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
(Decrease) increase in accrued interest payable - TRuPS	(62,510)	14,564	12,118
Other, net	3,720	4,763	4,356
Net cash provided by (used in) operating activities	1,379	122,965	56,182
Cash flows from financing activities:
Net cash used in financing activities	57,341	(125,120)	(174,362)
Net increase (decrease) in unrestricted cash	14,967	(328,411)	45,706
Cash and cash equivalents, beginning of year	190,435	518,846	473,140
Cash and cash equivalents, end of year	205,402	190,435	518,846
Supplemental disclosures of cash flow information:
Cash paid for interest on liabilities	83,688	9,540	17,493
First Banks, Inc. Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income attributable to First Banks, Inc.	21,655	241,744	26,278
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net income of subsidiaries	(32,208)	(218,409)	(41,745)
Dividends from subsidiaries	95,000	0	0
(Decrease) increase in accrued interest payable - TRuPS	(62,481)	14,977	14,771
Other, net	(2,214)	(39,192)	639
Net cash provided by (used in) operating activities	19,752	(880)	(57)
Cash flows from financing activities:
Payment of preferred stock dividends	0	0	0
Net cash used in financing activities	0	0	0
Net increase (decrease) in unrestricted cash	19,752	(880)	(57)
Cash and cash equivalents, beginning of year	1,864	2,744	2,801
Cash and cash equivalents, end of year	21,616	1,864	2,744
Supplemental disclosures of cash flow information:
Cash paid for interest on liabilities	$ 75,340	$ 0	$ 0