Investment Securities Narrative (Details) (USD $)	3 Months Ended		9 Months Ended											3 Months Ended		9 Months Ended		3 Months Ended	6 Months Ended	9 Months Ended				9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Oct. 01, 2012	Jul. 31, 2012	Dec. 31, 2011	Sep. 30, 2012 Equity Securities [Member]	Dec. 31, 2011 Equity Securities [Member]	Sep. 30, 2012 Equity Securities Financial Institution [Member]	Dec. 31, 2011 Equity Securities Financial Institution [Member]	Sep. 30, 2012 Equity Securities, Other [Member]	Dec. 31, 2011 Equity Securities, Other [Member]	Sep. 30, 2012 Auction Rate Securities [Member]	Sep. 30, 2011 Auction Rate Securities [Member]	Sep. 30, 2012 Auction Rate Securities [Member]	Dec. 31, 2011 Auction Rate Securities [Member]	Sep. 30, 2012 Auction Rate Securities [Member] External Credit Rating, Rated Above Investment Grade [Member]	Jun. 30, 2012 Auction Rate Securities [Member] External Credit Rating, Rated Above Investment Grade [Member]	Sep. 30, 2012 Auction Rate Securities [Member] Moody's, A3 Rating [Member]	Sep. 30, 2012 Auction Rate Securities [Member] Moody's, A2 Rating [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member] External Credit Rating, Rated Below Investment Grade [Member]	Sep. 30, 2012 Single-issuer Trust Preferred Securities [Member]	Sep. 30, 2012 Single-issuer Trust Preferred Securities [Member] External Credit Rating, Rated Below Investment Grade [Member]	Sep. 30, 2012 Single-issuer Trust Preferred Securities [Member] External Credit Rating, BBB [Member]
Statement of Investments [Line Items]
Available-for-sale Securities Pledged as Collateral	$ 1,900,000,000		$ 1,900,000,000				$ 1,800,000,000
Restricted equity securities issued by the Federal Home Loan Bank and Federal Reserve Bank								73,200,000	82,500,000
Available-for-sale Securities, Equity Securities										37,400,000	27,900,000	6,700,000	6,700,000
Amortized cost	2,744,829,000		2,744,829,000				2,633,226,000	113,838,000	117,486,000	34,000,000				188,378,000		188,378,000	240,852,000						5,400,000		22,900,000	5,600,000
Available for sale	2,789,684,000		2,789,684,000				2,673,298,000	117,318,000	117,050,000	37,400,000				160,062,000		160,062,000	225,211,000						5,000,000		21,600,000	4,100,000
SingleBankStockInvestment, cost basis	13,600,000		13,600,000		6,400,000	12,700,000
IndividualBankStockInvestmentPercentageOwnershipThreshold	5.00%		5.00%
BankStockInvestmentFairValue	14,800,000		14,800,000
PercentOwnershipInAnIndividualFinancialInstitution	40.00%		40.00%
IndividualBankStockInvestmentPercenttoTotalPortfolio	5.00%		5.00%
PercentageOwnshipInAnIndividualBankStockInvestment					7.20%
Other than Temporary Impairment Losses, Investments	43,000	509,000	100,000	1,601,000											292,000,000
AuctionRateSecurityCallsAtParValue														51,500,000		56,100,000
Carrying Value Action Rate Securities Above Investment Grade																		149,000,000
Percentage Action Rate Securities Above Investment Grade																			93.00%
Carrying Value Auction Rate Securities Rated Investment Grade																				21,000,000	94,000,000
Percentage Auction Rate Securities Investment Grade																				13.00%	59.00%
Carrying value auction rate securities below investment grade														11,000,000		11,000,000
Percentage Auction Rate Securities Below Investment Grade														7.00%		7.00%
US Government Guaranteed student loans below investment grade														8,000,000		8,000,000
Percentage US Government guaranteed student loans below investment grade														72.00%		72.00%
US Government Guaranteed student loan auction rate securities														156,000,000		156,000,000
US Government Guaranteed student loan auction rate securities percentage																98.00%
Auction Rate Certificates Not Subject To Any Additional Other Than Temporary Impairment Charges Fair Value	160,100,000		160,100,000
Unrealized Gain (Loss) on Securities																								(7,300,000)
Number of Trust Preferred Securities																						10	9		8
Available-for-sale Securities, Amortized Cost Basis	2,744,829,000		2,744,829,000				2,633,226,000	113,838,000	117,486,000	34,000,000				188,378,000		188,378,000	240,852,000						5,400,000		22,900,000	5,600,000
Securities available for sale	2,789,684,000		2,789,684,000				2,673,298,000	117,318,000	117,050,000	37,400,000				160,062,000		160,062,000	225,211,000						5,000,000		21,600,000	4,100,000
Pooled trust preferred securities actual weighted average cumulative defaults and deferrals			41.20%
Domestic Corporate debt securities	$ 106,100,000		$ 106,100,000