Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 460,217	[1]	$ 639,730	[2]	$ 552,663	[1]
Overnight investments	954,232	[1]	443,180	[2]	752,334	[1]
Investment securities available for sale	5,279,678	[1]	5,226,228	[2]	4,457,739	[1]
Investment securities held to maturity	1,229	[1]	1,342	[2]	1,688	[1]
Loans held for sale	86,351	[1]	86,333	[2]	73,457	[1]
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,621,327	[1]	1,809,235	[2]	2,183,869	[1]
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,509,080	[1]	11,576,115	[2]	11,489,529	[1]
Receivable from FDIC for loss share agreements	195,942	[1]	270,192	[2]	492,384	[1]	617,377
Income earned not collected	47,255	[1]	47,666	[2]	52,406	[1]
Stock issued by:
Deposits	18,064,921	[1]	18,086,025	[2]	17,759,492	[1]
Short-term borrowings	573,102	[1]	568,505	[2]	677,993	[1]
Long-term obligations	444,252	[1]	444,921	[2]	649,818	[1]
Payable to FDIC for Loss Share Agreements	98,870		101,641		82,033
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	460,217		639,730		552,663
Overnight investments	954,232		443,180		752,334
Investment securities available for sale	5,279,678		5,226,228		4,457,739
Investment securities held to maturity	1,229		1,342		1,688
Loans held for sale	86,351		86,333		73,457
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,524,854		1,669,263		2,097,752
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,332,534		11,397,069		11,303,146
Receivable from FDIC for loss share agreements	195,942	[3]	270,192	[3]	492,384	[3]
Income earned not collected	47,255		47,666		52,406
Stock issued by:
Preferred stock	46,397		40,768		0
Deposits	18,064,921		18,086,025		17,759,492
Short-term borrowings	573,102		568,505		677,993
Long-term obligations	444,252		444,921		649,818
Payable to FDIC for Loss Share Agreements	98,870		101,641		82,033
Accrued interest payable	6,653		9,353		21,486
Interest rate swap	9,583		10,398		10,325
Carrying Value | Investment In Federal Home Loan Bank Of Atlanta Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	28,789		36,139		41,043
Carrying Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	9,092		10,107		12,356
Carrying Value | Investment In Federal Home Loan Bank Of Seattle Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	4,370		4,410		4,490
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	460,217		639,730		552,663
Overnight investments	954,232		443,180		752,334
Investment securities available for sale	5,279,678		5,226,228		4,457,739
Investment securities held to maturity	1,322		1,448		1,844
Loans held for sale	88,116		87,654		75,342
Loans covered by loss share agreements, net of allowance for loan and lease losses	1,494,357		1,635,878		2,055,797
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,298,475		11,238,597		11,171,217
Receivable from FDIC for loss share agreements	104,684	[3]	100,161	[3]	297,963	[3]
Income earned not collected	47,255		47,666		52,406
Stock issued by:
Preferred stock	47,624		40,793		0
Deposits	18,099,371		18,126,893		17,810,831
Short-term borrowings	573,102		568,505		677,993
Long-term obligations	469,980		472,642		679,727
Payable to FDIC for Loss Share Agreements	119,473		125,065		95,643
Accrued interest payable	6,653		9,353		21,486
Interest rate swap	9,583		10,398		10,325
Fair Value | Investment In Federal Home Loan Bank Of Atlanta Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	28,789		36,139		41,043
Fair Value | Investment In Federal Home Loan Bank Of San Francisco Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	9,092		10,107		12,356
Fair Value | Investment In Federal Home Loan Bank Of Seattle Stock
Stock issued by:
Stock issued by Federal Home Loan Bank	$ 4,370		$ 4,410		$ 4,490

[1] Unaudited

[2] Derived from 2012 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.