REGULATORY CAPITAL AND OTHER REGULATORY MATTERS (Details Textual) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Interest paid on junior subordinated debentures in March 2014	$ 83,688,000	$ 9,540,000	$ 17,493,000
Net Deferred Tax Assets Attributable To Net Operating Loss And Tax Credit Carryforwards As A Percentage Of Total Net Deferred Tax Assets	87.00%
First Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to First Banks, Inc. by First Bank	95,000,000			70,000,000
First Banks, Inc. Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Interest paid on junior subordinated debentures in March 2014	75,340,000	0	0
Subordinated Debt [Member] | First Banks, Inc. Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Interest paid on junior subordinated debentures in March 2014				$ 66,400,000