BUSINESS SEGMENT RESULTS (Schedule of Business Segment Results) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance sheet information:
Investment securities	$ 2,351,931	$ 2,675,280	$ 2,470,704
Total loans	2,857,095	2,930,747	3,284,279
FRB and FHLB stock	27,357	27,329	27,078
Goodwill	0	125,267	125,267
Assets of discontinued operations	0	6,706	6,913
Total assets	5,918,983	6,509,126	6,608,913
Deposits	4,813,895	5,492,847	5,623,055
Other borrowings	43,143	26,025	51,170
Subordinated debentures	354,210	354,133	354,057
Liabilities of discontinued operations	0	155,711	174,737
Stockholders’ equity	488,256	299,959	263,671	307,295
Income statement information:
Interest income	172,810	200,803	231,059
Interest expense	24,104	29,611	43,638
Net interest income (loss)	148,706	171,192	187,421
Provision (benefit) for loan losses	(5,000)	2,000	69,000
Net interest income (loss) after provision (benefit) for loan losses	153,706	169,192	118,421
Noninterest income	65,120	65,978	61,924
Goodwill impairment	107,267	0	0
Amortization of intangible assets	0	0	3,024
Other noninterest expense	179,360	200,507	222,681
(Loss) income from continuing operations, before benefit for income taxes	(67,801)	34,663	(45,360)
(Benefit) provision for income taxes	(288,501)	(139)	(10,654)
Net income (loss) from continuing operations, net of tax	220,700	34,802	(34,706)
Income (loss) from discontinued operations, net of tax	21,223	(8,821)	(9,394)
Net income (loss)	241,923	25,981	(44,100)
Net income (loss) attributable to noncontrolling interest in subsidiary	179	(297)	(2,950)
Net income (loss) attributable to First Banks, Inc.	241,744	26,278	(41,150)
Corporate, Other and Intercompany Reclassifications
Balance sheet information:
Investment securities	0	0	0
Total loans	0	0	0
FRB and FHLB stock	0	0	0
Goodwill	0	0	0
Assets of discontinued operations	0	0	0
Total assets	53,823	13,900	15,398
Deposits	(1,897)	(2,777)	(2,834)
Other borrowings	0	0	0
Subordinated debentures	354,210	354,133	354,057
Liabilities of discontinued operations	0	0	0
Stockholders’ equity	(443,305)	(451,293)	(416,954)
Income statement information:
Interest income	0	121	85
Interest expense	15,050	14,838	13,612
Net interest income (loss)	(15,050)	(14,717)	(13,527)
Provision (benefit) for loan losses	0	0	0
Net interest income (loss) after provision (benefit) for loan losses	(15,050)	(14,717)	(13,527)
Noninterest income	454	405	219
Goodwill impairment	0	0	0
Amortization of intangible assets	0	0	0
Other noninterest expense	910	1,510	(378)
(Loss) income from continuing operations, before benefit for income taxes	(15,506)	(15,822)	(12,930)
(Benefit) provision for income taxes	(39,364)	(369)	(46)
Net income (loss) from continuing operations, net of tax	23,858	(15,453)	(12,884)
Income (loss) from discontinued operations, net of tax	0	0	0
Net income (loss)	23,858	(15,453)	(12,884)
Net income (loss) attributable to noncontrolling interest in subsidiary	0	0	0
Net income (loss) attributable to First Banks, Inc.	23,858	(15,453)	(12,884)
Operating Segments [Member] | First Bank
Balance sheet information:
Investment securities	2,351,931	2,675,280	2,470,704
Total loans	2,857,095	2,930,747	3,284,279
FRB and FHLB stock	27,357	27,329	27,078
Goodwill	0	125,267	125,267
Assets of discontinued operations	0	6,706	6,913
Total assets	5,865,160	6,495,226	6,593,515
Deposits	4,815,792	5,495,624	5,625,889
Other borrowings	43,143	26,025	51,170
Subordinated debentures	0	0	0
Liabilities of discontinued operations	0	155,711	174,737
Stockholders’ equity	931,561	751,252	680,625
Income statement information:
Interest income	172,810	200,682	230,974
Interest expense	9,054	14,773	30,026
Net interest income (loss)	163,756	185,909	200,948
Provision (benefit) for loan losses	(5,000)	2,000	69,000
Net interest income (loss) after provision (benefit) for loan losses	168,756	183,909	131,948
Noninterest income	64,666	65,573	61,705
Goodwill impairment	107,267	0	0
Amortization of intangible assets	0	0	3,024
Other noninterest expense	178,450	198,997	223,059
(Loss) income from continuing operations, before benefit for income taxes	(52,295)	50,485	(32,430)
(Benefit) provision for income taxes	(249,137)	230	(10,608)
Net income (loss) from continuing operations, net of tax	196,842	50,255	(21,822)
Income (loss) from discontinued operations, net of tax	21,223	(8,821)	(9,394)
Net income (loss)	218,065	41,434	(31,216)
Net income (loss) attributable to noncontrolling interest in subsidiary	179	(297)	(2,950)
Net income (loss) attributable to First Banks, Inc.	$ 217,886	$ 41,731	$ (28,266)