Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Jun. 30, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 606,107	[1]		$ 590,801	[2]	$ 539,337	[1]
Overnight investments	688,196	[1]		434,975	[2]	410,002	[1]
Investment securities available for sale	5,012,041	[1]		4,056,423	[2]	3,994,825	[1]
Investment securities held to maturity	1,459	[1]		1,822	[2]	1,943	[1]
Loans held for sale	78,610	[1]		92,539	[2]	78,178	[1]
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,897,097	[1]		2,362,152	[2]	2,557,450	[1]
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,455,233	[1]		11,581,637	[2]	11,603,526	[1]
Receivable from FDIC for loss share agreements	243,893	[1]	313,978	539,511	[2]	607,907	[1]	522,507	623,261
Income earned not collected	51,565	[1]		42,216	[2]	43,886	[1]
Stock issued by:
Stock issued by Federal Home Loan Bank	53,735					61,397
Deposits	17,893,215	[1]		17,577,274	[2]	17,663,275	[1]
Short-term borrowings	677,773	[1]		615,222	[2]	600,384	[1]
Long-term obligations	472,170	[1]		687,599	[2]	744,839	[1]
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	606,107			590,801		539,337
Overnight investments	688,196			434,975		410,002
Investment securities available for sale	5,012,041			4,056,423		3,994,825
Investment securities held to maturity	1,459			1,822		1,943
Loans held for sale	78,610			92,539		78,178
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,806,593			2,272,891		2,482,400
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,269,183			11,400,754		11,424,392
Receivable from FDIC for loss share agreements	243,893	[3]		539,511	[3]	607,907	[3]
Income earned not collected	51,565			42,216		43,886
Stock issued by:
Preferred stock	20,320			0		0
Deposits	17,893,215			17,577,274		17,663,275
Short-term borrowings	677,773			615,222		600,384
Long-term obligations	472,170			687,599		744,839
Accrued interest payable	11,145			23,719		22,153
Interest rate swap	11,170			10,714		13,531
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		43,302
Carrying Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	11,140			12,976		13,605
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	606,107			590,801		539,337
Overnight investments	688,196			434,975		410,002
Investment securities available for sale	5,012,041			4,056,423		3,994,825
Investment securities held to maturity	1,583			1,980		2,108
Loans held for sale	80,357			93,235		78,178
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,770,250			2,236,343		2,469,613
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,127,286			11,312,900		11,329,623
Receivable from FDIC for loss share agreements	50,382	[3]		446,172	[3]	500,745	[3]
Income earned not collected	51,565			42,216		43,886
Stock issued by:
Preferred stock	20,345			0		0
Deposits	17,939,303			17,638,359		17,712,240
Short-term borrowings	677,773			615,222		600,384
Long-term obligations	503,369			719,999		774,799
Accrued interest payable	11,145			23,719		22,153
Interest rate swap	11,170			10,714		13,531
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		43,302
Fair Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	11,140			12,976		13,605
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 receivable related to accretable yield in prospective periods.