Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2012		Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 542,645	[1]		$ 639,730	[2]	$ 571,004	[1]
Overnight investments	1,039,925	[1]		443,180	[2]	984,536	[1]
Investment securities available for sale	5,184,976	[1]		5,226,228	[2]	4,634,248	[1]
Investment securities held to maturity	1,130	[1]		1,342	[2]	1,578	[1]
Loans held for sale	62,497	[1]		86,333	[2]	76,374	[1]
Receivable from FDIC for loss share agreements	158,013	[1]	195,942	270,192	[2]	405,626	[1]	492,384	617,377
Income earned not collected	45,567	[1]		47,666	[2]	49,743	[1]
Stock issued by:
Deposits	18,018,015	[1]		18,086,025	[2]	17,801,646	[1]
Payable to FDIC for loss share agreements	101,652			101,641		91,648
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	542,645			639,730		571,004
Overnight investments	1,039,925			443,180		984,536
Investment securities available for sale	5,184,976			5,226,228		4,634,248
Investment securities held to maturity	1,130			1,342		1,578
Loans held for sale	62,497			86,333		76,374
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,366,802			1,669,263		1,911,554
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,473,687			11,397,069		11,277,326
Receivable from FDIC for loss share agreements	158,013	[3]		270,192	[3]	405,626	[3]
Income earned not collected	45,567			47,666		49,743
Stock issued by:
Preferred stock	41,665			40,768		0
Deposits	18,018,015			18,086,025		17,801,646
Short-term borrowings	581,937			568,505		700,299
Long-term obligations	443,313			444,921		644,682
Payable to FDIC for loss share agreements	101,652			101,641		91,648
Accrued interest payable	9,208			9,353		23,093
Interest rate swap	8,196			10,398		11,020
Carrying Value | Investment In Federal Home Loan Bank Of Atlanta Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	28,788			36,139		38,105
Carrying Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	8,061			10,107		11,746
Carrying Value | Investment In Federal Home Loan Bank Of Seattle Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	4,330			4,410		4,490
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	542,645			639,730		571,004
Overnight investments	1,039,925			443,180		984,536
Investment securities available for sale	5,184,976			5,226,228		4,634,248
Investment securities held to maturity	1,200			1,448		1,714
Loans held for sale	64,262			87,654		78,139
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,339,466			1,635,878		1,873,323
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,317,282			11,238,597		11,200,523
Receivable from FDIC for loss share agreements	71,353	[3]		100,161	[3]	297,963	[3]
Income earned not collected	45,567			47,666		49,743
Stock issued by:
Preferred stock	42,898			40,793		0
Deposits	18,049,241			18,126,893		17,854,346
Short-term borrowings	581,937			568,505		700,299
Long-term obligations	463,244			472,642		677,372
Payable to FDIC for loss share agreements	117,891			125,065		110,373
Accrued interest payable	9,208			9,353		23,093
Interest rate swap	8,196			10,398		11,020
Fair Value | Investment In Federal Home Loan Bank Of Atlanta Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	28,788			36,139		38,105
Fair Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	8,061			10,107		11,746
Fair Value | Investment In Federal Home Loan Bank Of Seattle Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	$ 4,330			$ 4,410		$ 4,490

[1] Unaudited

[2] Derived from 2012 Annual Report on Form 10-K.

[3] The fair value of the FDIC receivable excludes receivable related to accretable yield to be amortized in prospective periods.