Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2011		Jun. 30, 2011		Mar. 31, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 571,004	[1]		$ 590,801	[2]	$ 537,717	[1]
Overnight investments	984,536	[1]		434,975	[2]	741,654	[1]
Investment securities available for sale	4,634,248	[1]		4,056,423	[2]	4,014,241	[1]
Investment securities held to maturity	1,578	[1]		1,822	[2]	2,098	[1]
Loans held for sale	76,374	[1]		92,539	[2]	56,004	[1]
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,999,351	[1]		2,362,152	[2]	2,399,738	[1]
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,462,458	[1]		11,581,637	[2]	11,528,854	[1]
Receivable from FDIC for loss share agreements	313,978	[1]	410,351	539,511	[2]	522,507	[1]	624,322	623,261
Income earned not collected	49,743	[1]		42,216	[2]	50,876	[1]
Stock issued by:
Stock issued by Federal Home Loan Bank	54,341					63,730
Deposits	17,801,646	[1]		17,577,274	[2]	17,662,966	[1]
Short-term borrowings	700,299	[1]		615,222	[2]	655,808	[1]
Long-term obligations	644,682	[1]		687,599	[2]	792,661	[1]
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	571,004			590,801		537,717
Overnight investments	984,536			434,975		741,654
Investment securities available for sale	4,634,248			4,056,423		4,014,241
Investment securities held to maturity	1,578			1,822		2,098
Loans held for sale	76,374			92,539		56,004
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,911,554			2,272,891		2,330,303
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,277,326			11,400,754		11,348,239
Receivable from FDIC for loss share agreements	313,978	[3]		539,511	[3]	522,507	[3]
Income earned not collected	49,743			42,216		50,876
Stock issued by:
Deposits	17,801,646			17,577,274		17,662,966
Short-term borrowings	700,299			615,222		655,808
Long-term obligations	644,682			687,599		792,661
Accrued interest payable	23,093			23,719		27,930
Interest rate swap	11,020			10,714		9,800
Carrying Value | Investment In Federal Home Loan Bank Of Atlanta Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	38,105			41,042		45,002
Carrying Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	11,746			12,976		14,238
Carrying Value | Investment In Federal Home Loan Bank Of Seattle Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	4,490			4,490		4,490
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	571,004			590,801		537,717
Overnight investments	984,536			434,975		741,654
Investment securities available for sale	4,634,248			4,056,423		4,014,241
Investment securities held to maturity	1,715			1,980		2,278
Loans held for sale	78,139			93,235		56,004
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,873,323			2,236,343		2,318,304
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,200,523			11,312,900		11,213,325
Receivable from FDIC for loss share agreements	297,963	[3]		446,172	[3]	529,514	[3]
Income earned not collected	49,743			42,216		50,876
Stock issued by:
Deposits	17,854,346			17,638,359		17,711,225
Short-term borrowings	700,299			615,222		655,808
Long-term obligations	677,372			719,999		807,407
Accrued interest payable	23,093			23,719		27,930
Interest rate swap	11,020			10,714		9,800
Fair Value | Investment In Federal Home Loan Bank Of Atlanta Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	38,105			41,042		45,002
Fair Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	11,746			12,976		14,238
Fair Value | Investment In Federal Home Loan Bank Of Seattle Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	$ 4,490			$ 4,490		$ 4,490

[1] Unaudited

[2] Derived from 2011 Annual Report on Form 10-K.

[3] The fair value of the receivable from FDIC for loss share agreements excludes amounts expected to be recovered through accretion income in prospective periods.