COVERED ASSETS AND FDIC INDEMNIFICATION ASSET (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for loan losses disclosures
Additional advances under shared-loss agreements	$ 431,700,000	$ 583,800,000
Provision for covered loans	(5,016,000)	(2,422,000)	(4,225,000)
Total allowance allocated to additional advances	5,200,000	6,600,000
Percentage of allowance allocated to additional advances	2.20%	3.10%
Residential
Allowance for loan losses disclosures
Additional advances under shared-loss agreements	11,500,000	12,700,000
Total allowance allocated to additional advances	87,000	70,000
Commercial Real Estate ("CRE")
Allowance for loan losses disclosures
Additional advances under shared-loss agreements	83,400,000	149,100,000
Total allowance allocated to additional advances	2,500,000	4,000,000
Commercial and Industrial ("C&I")
Allowance for loan losses disclosures
Additional advances under shared-loss agreements	302,300,000	390,300,000
Total allowance allocated to additional advances	2,400,000	2,400,000
Consumer
Allowance for loan losses disclosures
Additional advances under shared-loss agreements	34,500,000	31,600,000
Total allowance allocated to additional advances	194,000	174,000
Specific covered loans outside of the scope of ASC 310-30
Allowance for loan losses disclosures
Charge-offs	6,500,000
Provision for covered loans	5,000,000	2,400,000	4,200,000
Specific covered loans outside of the scope of ASC 310-30 | Commercial Real Estate ("CRE")
Allowance for loan losses disclosures
Charge-offs	1,500,000
Specific covered loans outside of the scope of ASC 310-30 | Commercial and Industrial ("C&I")
Allowance for loan losses disclosures
Charge-offs	$ 5,000,000