EARNINGS (LOSS) PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Class of Stock [Line Items]
Net income from continuing operations attributable to First Banks, Inc.	$ 8,033	$ 8,379
Preferred stock dividends declared and undeclared	(4,881)	(4,627)
Accretion of discount on preferred stock	(898)	(884)
Net income from continuing operations attributable to common stockholders	2,254	2,868
Net loss from discontinued operations attributable to common stockholders	(1,323)	(1,481)
Net income available to common stockholders	931	1,387
Weighted average shares of common stock outstanding (in shares)	23,661	23,661
Basic earnings per common share - continuing operations (in dollars per share)	$ 95.27	$ 121.23
Basic loss per common share - discontinued operations (in dollars per share)	$ (55.92)	$ (62.60)
Basic earnings per common share (in dollars per share)	$ 39.35	$ 58.63
Net income from continuing operations attributable to common stockholders	2,254	2,868
Net loss from discontinued operations attributable to common stockholders	(1,323)	(1,481)
Diluted income available to First Banks, Inc. common stockholders	931	1,387
Weighted average diluted shares of common stock outstanding (in shares)	23,661	23,661
Diluted earnings per common share - continuing operations (in dollars per share)	$ 95.27	$ 121.23
Diluted loss per common share - discontinued operations (in dollars per share)	$ (55.92)	$ (62.60)
Diluted earnings per common share (in dollars per share)	$ 39.35	$ 58.63
Class A Convertible Adjustable Rate Preferred Stock [Member]
Class of Stock [Line Items]
Effect of diluted securities - Class A convertible preferred stock	$ 0	$ 0
Effect of diluted securities - Class A convertible preferred stock (in shares)	0	0