PARENT COMPANY ONLY FINANCIAL INFORMATION (CONDENSED STATEMENTS OF CASH FLOWS) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Net income (loss) attributable to First Banks, Inc.	$ 26,278	$ (41,150)	$ (191,737)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Other, net	4,356	20,945	11,785
Net cash provided by operating activities	56,182	116,353	69,571
Cash flows from investing activities:
Net cash provided by (used in) investing activities	163,886	8,785	(699,109)
Cash flows from financing activities:
Net cash used in financing activities	(174,362)	(647,756)	(890,955)
Net increase (decrease) in cash and cash equivalents	45,706	(522,618)	(1,520,493)
Cash and cash equivalents, beginning of year	473,140	995,758	2,516,251
Cash and cash equivalents, end of year	518,846	473,140	995,758
Noncash investing activities:
Cash paid for interest	17,982	36,649	71,941
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income (loss) attributable to First Banks, Inc.	26,278	(41,150)	(191,737)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net (income) loss of subsidiaries	(41,745)	28,290	178,474
Other, net	15,410	12,042	6,012
Net cash provided by operating activities	(57)	(818)	(7,251)
Cash flows from investing activities:
Decrease in available-for-sale investment securities	0	0	3,570
Net cash provided by (used in) investing activities	0	0	3,570
Cash flows from financing activities:
Capital contributions to subsidiaries	0	0	(100)
Payment of preferred stock dividends	0	0	0
Net cash used in financing activities	0	0	(100)
Net increase (decrease) in cash and cash equivalents	(57)	(818)	(3,781)
Cash and cash equivalents, beginning of year	2,801	3,619	7,400
Cash and cash equivalents, end of year	2,744	2,801	3,619
Noncash investing activities:
Cash paid for interest	$ 0	$ 0	$ 0