NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 13) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	$ 234,535		$ 216,523		$ 216,523
Provision for loan losses	4,327		18,100		65,184
Allowance for unfunded loan commitments and letters of credit	716				1,563
Charge-offs	(3,055)				(64,912)
Recoveries	2,383				16,177
Net charge-offs	(672)		(10,300)		(48,735)
Ending balance	238,906				234,535
Ending balance allocated to:
Loans individually evaluated for impairment	12,633				11,527
Loans collectively evaluated for impairment	224,281				223,008
Covered loans acquired with deteriorated credit quality	1,992	[1]
Ending balance	238,906				234,535
Residential
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	49,349		52,180		52,180
Provision for loan losses	(2,926)				3,255
Charge-offs	(311)				(7,700)
Recoveries	768				1,614
Net charge-offs	457				(6,086)
Ending balance	46,880				49,349
Ending balance allocated to:
Loans individually evaluated for impairment	1,037				3,131
Loans collectively evaluated for impairment	45,843				46,218
Ending balance	46,880				49,349
Commercial Real Estate ("CRE")
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	69,856		66,457		66,457
Provision for loan losses	3,818				20,977
Charge-offs	(1,005)				(27,060)
Recoveries	289				9,482
Net charge-offs	(716)				(17,578)
Ending balance	72,958				69,856
Ending balance allocated to:
Loans individually evaluated for impairment	6,858				5,561
Loans collectively evaluated for impairment	66,100				64,295
Ending balance	72,958				69,856
Commercial and Industrial ("C&I")
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	105,376		87,020		87,020
Provision for loan losses	(2,300)				35,204
Charge-offs	(1,261)				(21,818)
Recoveries	531				4,970
Net charge-offs	(730)				(16,848)
Ending balance	102,346				105,376
Ending balance allocated to:
Loans individually evaluated for impairment	4,734				2,835
Loans collectively evaluated for impairment	97,612				102,541
Ending balance	102,346				105,376
Consumer
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	4,801		4,219		4,219
Provision for loan losses	1,362				2,295
Charge-offs	(346)				(1,824)
Recoveries	795				111
Net charge-offs	449				(1,713)
Ending balance	6,612				4,801
Ending balance allocated to:
Loans individually evaluated for impairment	4
Loans collectively evaluated for impairment	6,608				4,801
Ending balance	6,612				4,801
Covered Loans under ASC 310-10 Subject to Allowance for Loan Losses
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	5,153	[2]	6,647	[2]	6,647	[2]
Provision for loan losses	3,097	[2]			5,016	[2]
Charge-offs	(132)	[2]			(6,510)	[2]
Net charge-offs	(132)	[2]			(6,510)	[2]
Ending balance	8,118	[2]			5,153	[2]
Ending balance allocated to:
Loans collectively evaluated for impairment	8,118	[2]			5,153	[2]
Ending balance	8,118	[2]			5,153	[2]
Covered Loans under ASC 310-30 Subject to Allowance for Loan Losses
Financing Receivable Allowance for Credit Losses Roll Forward
Provision for loan losses	1,992
Ending balance	1,992
Ending balance allocated to:
Covered loans acquired with deteriorated credit quality	1,992	[1]
Ending balance	1,992
Unallocated
Financing Receivable Allowance for Credit Losses Roll Forward
Provision for loan losses	(716)				(1,563)
Allowance for unfunded loan commitments and letters of credit	$ 716				$ 1,563

[1] The Company has elected to account for covered loans acquired in the FDIC-assisted acquisitions under ASC 310-30, excluding any additional advances subsequent to acquisition date.

[2] This allowance is related to drawdowns on commitments that were in existence as of the acquisition dates of WFIB and UCB and, therefore, are covered under the shared-loss agreements with the FDIC. Allowance on these subsequent drawdownsis accounted for as part of the allowance for loan losses.