Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011		Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 552,663	[1]	$ 590,801	[2]	$ 406,252	[1]
Overnight investments	752,334	[1]	434,975	[2]	585,286	[1]
Investment securities available for sale	4,457,739	[1]	4,056,423	[2]	4,202,016	[1]
Investment securities held to maturity	1,688	[1]	1,822	[2]	2,341	[1]
Loans held for sale	73,457	[1]	92,539	[2]	48,222	[1]
Loans covered by loss share agreements, net of allowance for loan and lease losses	2,183,869	[1]	2,362,152	[2]	2,658,134	[1]
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,489,529	[1]	11,581,637	[2]	11,392,351	[1]
Receivable from FDIC for loss share agreements	410,351	[1]	539,511	[2]	624,322	[1]	623,261
Income earned not collected	52,406	[1]	42,216	[2]	98,501	[1]
Stock issued by:
Stock issued by Federal Home Loan Bank	57,889				66,488
Deposits	17,759,492	[1]	17,577,274	[2]	17,811,736	[1]
Short-term borrowings	677,993	[1]	615,222	[2]	666,417	[1]
Long-term obligations	649,818	[1]	687,599	[2]	801,081	[1]
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	552,663		590,801		406,252
Overnight investments	752,334		434,975		585,286
Investment securities available for sale	4,457,739		4,056,423		4,202,016
Investment securities held to maturity	1,688		1,822		2,341
Loans held for sale	73,457		92,539		48,222
Loans covered by loss share agreements, net of allowance for loan and lease losses	2,097,752		2,272,891		2,603,505
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,303,146		11,400,754		11,214,383
Receivable from FDIC for loss share agreements	410,351	[3]	539,511	[3]	624,322	[3]
Income earned not collected	52,406		42,216		98,501
Stock issued by:
Deposits	17,759,492		17,577,274		17,811,736
Short-term borrowings	677,993		615,222		666,417
Long-term obligations	649,818		687,599		801,081
Accrued interest payable	21,486		23,719		27,930
Interest rate swap	10,325		10,714		7,775
Carrying Value [Member] | Investment In Federal Home Loan Bank Of Atlanta Stock [Member]
Stock issued by:
Stock issued by Federal Home Loan Bank	41,043		41,042		47,123
Carrying Value [Member] | Investment In Federal Home Loan Bank Of San Francisco Stock [Member]
Stock issued by:
Stock issued by Federal Home Loan Bank	12,356		12,976		14,875
Carrying Value [Member] | Investment In Federal Home Loan Bank Of Seattle Stock [Member]
Stock issued by:
Stock issued by Federal Home Loan Bank	4,490		4,490		4,490
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	552,663		590,801		406,252
Overnight investments	752,334		434,975		585,286
Investment securities available for sale	4,457,739		4,056,423		4,202,016
Investment securities held to maturity	1,844		1,980		2,537
Loans held for sale	75,342		93,235		48,222
Loans covered by loss share agreements, net of allowance for loan and lease losses	2,055,797		2,236,343		2,590,214
Loans and leases not covered by loss share agreements, net of allowance for loan and lease losses	11,171,217		11,312,900		11,062,010
Receivable from FDIC for loss share agreements	297,963	[3]	446,172	[3]	557,356	[3]
Income earned not collected	52,406		42,216		98,501
Stock issued by:
Deposits	17,810,831		17,638,359		17,862,769
Short-term borrowings	677,993		615,222		666,417
Long-term obligations	679,727		719,999		813,652
Accrued interest payable	21,486		23,719		27,930
Interest rate swap	10,325		10,714		7,775
Fair Value [Member] | Investment In Federal Home Loan Bank Of Atlanta Stock [Member]
Stock issued by:
Stock issued by Federal Home Loan Bank	41,043		41,042		47,123
Fair Value [Member] | Investment In Federal Home Loan Bank Of San Francisco Stock [Member]
Stock issued by:
Stock issued by Federal Home Loan Bank	12,356		12,976		14,875
Fair Value [Member] | Investment In Federal Home Loan Bank Of Seattle Stock [Member]
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.