SUBORDINATED DEBENTURES (Textual) (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014 trust installment	Dec. 31, 2013 installment	Dec. 31, 2012	Mar. 31, 2014	Aug. 10, 2009
Debt Instrument [Line Items]
Number of trusts created for issuing trust preferred securities	13
Percent of principal amount callable at call date	100.00%
Distributions accrued on junior subordinated debentures	$ 12,900,000	$ 15,000,000	$ 14,800,000
Trust preferred securities value					345,000,000
Number of quarterly periods for deferral of cash interest payments on junior subordinated debt		18
Interest paid on junior subordinated debentures in March 2014	83,688,000	9,540,000	17,493,000
Regularly Scheduled Deferred Interest Payments Accrued [Member]
Debt Instrument [Line Items]
Interest payable		56,000,000
Additional Deferred Interest Payments Accrued [Member]
Debt Instrument [Line Items]
Interest payable		6,700,000
First Bank [Member]
Debt Instrument [Line Items]
Cash dividends paid to First Banks, Inc. by First Bank	95,000,000			70,000,000
First Banks, Inc. Parent Company [Member]
Debt Instrument [Line Items]
Interest payable	374,000	62,855,000
Interest paid on junior subordinated debentures in March 2014	75,340,000	0	0
Subordinated Debt [Member] | First Banks, Inc. Parent Company [Member]
Debt Instrument [Line Items]
Interest paid on junior subordinated debentures in March 2014				$ 66,400,000