CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) [Abstract]
Net income (loss)	$ 6,838	$ (6,083)
Other comprehensive income (loss):
Unrealized gains on available-for-sale investment securities, net of tax	6,718	2,364
Reclassification adjustment for available-for-sale investment securities gains included in net income (loss), net of tax	(339)	(335)
Reclassification adjustment for deferred tax asset valuation allowance on investment securities	3,435	1,093
Amortization of net loss related to pension liability, net of tax	21	15
Reclassification adjustment for deferred tax asset valuation allowance on pension liability	15	11
Other comprehensive income	9,850	3,148
Comprehensive income (loss)	16,688	(2,935)
Comprehensive (loss) income attributable to noncontrolling interest in subsidiary	(60)	65
Comprehensive income (loss) attributable to First Banks, Inc.	$ 16,748	$ (3,000)