EARNINGS (LOSS) PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income (loss) from continuing operations attributable to First Banks, Inc.	$ 10,802	$ 910	$ 30,212	$ (16,376)
Preferred stock dividends declared and undeclared	(4,753)	(4,506)	(14,070)	(13,341)
Accretion of discount on preferred stock	(893)	(874)	(2,660)	(2,593)
Net income (loss) from continuing operations attributable to common stockholders	5,156	(4,470)	13,482	(32,310)
Net loss from discontinued operations attributable to common stockholders	(2,329)	(2,984)	(7,333)	(8,895)
Net income (loss) available to First Banks, Inc. common stockholders	2,827	(7,454)	6,149	(41,205)
Weighted average shares of common stock outstanding (in shares)	23,661	23,661	23,661	23,661
Basic earnings (loss) per common share continuing operations (in dollars per share)	$ 217.91	$ (188.89)	$ 569.81	$ (1,365.48)
Basic loss per common share discontinued operations (in dollars per share)	$ (98.43)	$ (126.12)	$ (309.92)	$ (375.94)
Basic earnings (loss) per common share (in dollars per share)	$ 119.48	$ (315.01)	$ 259.89	$ (1,741.42)
Net income (loss) from continuing operations attributable to common stockholders	5,156	(4,470)	13,482	(32,310)
Net loss from discontinued operations attributable to common stockholders	(2,329)	(2,984)	(7,333)	(8,895)
Net income (loss) available to First Banks, Inc. common stockholders	2,827	(7,454)	6,149	(41,205)
Diluted income (loss) available to First Banks, Inc. common stockholders	2,827	(7,454)	6,149	(41,205)
Weighted average shares of common stock outstanding (in shares)	23,661	23,661	23,661	23,661
Weighted average diluted shares of common stock outstanding (in dollars per share)	23,661	23,661	23,661	23,661
Diluted earnings (loss) per common share - continuing operations (in dollars per share)	$ 217.91	$ (188.89)	$ 569.81	$ (1,365.48)
Diluted loss per common share - discontinued operations (in dollars per share)	$ (98.43)	$ (126.12)	$ (309.92)	$ (375.94)
Diluted earnings (loss) per common share (in dollars per share)	$ 119.48	$ (315.01)	$ 259.89	$ (1,741.42)
Class A Convertible Adjustable Rate Preferred Stock [Member]
Class A convertible preferred stock	0	0	0	0
Class A convertible preferred stock	$ 0	$ 0	$ 0	$ 0