EARNINGS (LOSS) PER COMMON SHARE (Earnings Per Share Reconciliation) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Class of Stock [Line Items]
Net income (loss) from continuing operations attributable to First Banks, Inc.	$ 31,801	$ (34,691)	$ (195,299)
Preferred stock dividends declared and undeclared	(18,886)	(17,908)	(16,980)
Accretion of discount on preferred stock	(3,554)	(3,466)	(3,381)
Net income (loss) from continuing operations attributable to common stockholders	9,361	(56,065)	(215,660)
Net (loss) income from discontinued operations attributable to common stockholders	(5,523)	(6,459)	3,562
Net income (loss) available to common stockholders	3,838	(62,524)	(212,098)
Weighted average shares of common stock outstanding	23,661	23,661	23,661
Basic earnings (loss) per common share – continuing operations	$ 395.64	$ (2,369.48)	$ (9,114.61)
Basic (loss) earnings per common share – discontinued operations	$ (233.42)	$ (272.98)	$ 150.54
Basic earnings (loss) per common share	$ 162.22	$ (2,642.46)	$ (8,964.07)
Net income (loss) from continuing operations attributable to common stockholders	9,361	(56,065)	(215,660)
Net (loss) income from discontinued operations attributable to common stockholders	(5,523)	(6,459)	3,562
Net income (loss) available to First Banks, Inc. common stockholders	3,838	(62,524)	(212,098)
Weighted average shares of common stock outstanding	23,661	23,661	23,661
Diluted earnings (loss) per common share – continuing operations	$ 395.64	$ (2,369.48)	$ (9,114.61)
Diluted (loss) earnings per common share – discontinued operations	$ (233.42)	$ (272.98)	$ 150.54
Diluted earnings (loss) per common share	$ 162.22	$ (2,642.46)	$ (8,964.07)
Class A convertible preferred stock
Class of Stock [Line Items]
Effect of dilutive securities – Class A convertible preferred stock	$ 0	$ 0	$ 0
Effect of dilutive securities – Class A convertible preferred stock	0	0	0