LOANS RECEIVABLE AND ALLOWANCE FOR CREDIT LOSSES (Details 11) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Net payable to the FDIC	$ 0	$ 96,100
FDIC indemnification asset/(Payable to FDIC, net)
Beginning balance	(96,106)	74,708	$ 316,313
Amortization	(3,906)	(101,638)	(99,055)
Reductions	(10,307)	(33,595)	(95,536)
Estimate of FDIC repayment	110,319	(35,581)	(47,014)
Ending balance	0	(96,106)	74,708
WFIB and UCB [Member]
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Payment for early termination of shared-loss agreements	125,500
Loans Receivable
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Total loans	23,659,761	21,727,145
Loans covered under shared-loss agreements		1,480,000
Loans Receivable | PCI Loans
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Total loans	970,754	1,322,113
Loans covered under shared-loss agreements		1,230,000
Changes in the accretable yield for the PCI loans
Beginning balance	311,688	461,545	556,986
Addition	0	6,745	0
Accretion	(107,442)	(219,169)	(347,010)
Changes in expected cash flows	10,661	62,567	251,569
Ending balance	$ 214,907	$ 311,688	$ 461,545