COVERED ASSETS AND FDIC INDEMNIFICATION ASSET, FDIC Indemnification Asset and FDIC Receivable (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Dec. 31, 2010
FDIC indemnification asset activitis [Rollforward]
Balance at beginning of period	$ 630,437,000		$ 939,913,000		$ 785,035,000		$ 1,084,716,000
Addition due to WFIB acquisition	0		0		0		41,131,000
(Amortization) Accretion	(14,325,000)		7,118,000		(48,034,000)		29,210,000
Reductions	(43,349,000)	[1],[2]	(79,370,000)	[1],[2]	(164,238,000)	[1],[2]	(287,396,000)	[1],[2]
Estimate of FDIC repayment	(3,606,000)	[3]	0	[3]	(3,606,000)	[3]	0	[3]
Balance at end of period	569,157,000		867,661,000		569,157,000		867,661,000
Amount of chargeoffs recoverable from the FDIC	18,400,000		70,800,000		92,800,000		188,800,000
FDIC Receivable [Abstract]
FDIC loss sharing receivable	$ 51,800,000				$ 51,800,000				$ 62,600,000
Percentage of any reimbursable expense recorded as noninterest income (in hundredths)	80.00%				80.00%				80.00%
Percentage of actual expense paid by the Company (in hundredths)	20.00%				20.00%				20.00%
Percentage of reimbursable expenses recorded as non-interest expense (in hundredths)	100.00%				100.00%				100.00%

[1] For the three and nine months ended September 30, 2011, the reduction amounts of $43.3 million and $164.2 million, respectively, include charge-offs, of which $18.4 million and $92.8 million, respectively, of these charge-offs are recoverable from the FDIC and recorded in other assets. For the three and nine months ended September 30, 2010, the reduction amounts of $79.4 million and $287.4 million, respectively, also include charge-offs, of which $70.8 million and $188.8 million, respectively, is recoverable from the FDIC and recorded in other assets.

[2] Reductions relate to cash flows received from principal amortization, partial prepayments, loan payoffs and loan sales.

[3] This represents the change in the calculated estimate the company will be required to pay the FDIC at the end of the FDIC loss share agreements, due to lower thresholds of losses.