Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities Available-for-sale	$ 2,501,198		$ 2,568,434
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	260,389		218,540
Interest-Rate Deposits with Other Banks	225,428		163,988
Loans Held-for-sale	24,417	[1]	21,351	[1]
Securities Available-for-sale	2,501,198	[1]	2,568,434	[1]
Loans, net of unearned income	12,733,792	[1]	12,782,220	[1]
Accrued Interest Receivable	43,376		44,037
Other Financial Assets	149,453	[1]	146,933	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,667,357		9,573,264
Time Deposit Liabilities, Fair Value Disclosure	3,002,560		2,917,922
Short-term borrowings	1,069,684		1,258,629
Accrued interest payable	16,972		15,218
Other Financial Liabilities	133,848	[1]	124,440	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	883,461		883,584
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	260,389		218,540
Interest-Rate Deposits with Other Banks	225,428		163,988
Loans Held-for-sale	24,417	[1]	21,351	[1]
Securities Available-for-sale	2,501,198	[1]	2,568,434	[1]
Loans, net of unearned income	12,628,983	[1]	12,688,774	[1]
Accrued Interest Receivable	43,376		44,037
Other Financial Assets	149,453	[1]	146,933	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,667,357		9,573,264
Time Deposit Liabilities, Fair Value Disclosure	3,011,698		2,927,374
Short-term borrowings	1,069,684		1,258,629
Accrued interest payable	16,972		15,218
Other Financial Liabilities	133,848	[1]	124,440	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	881,197		875,984
Interest-bearing Deposits [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	81,634		84,173
Interest-bearing Deposits [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	$ 81,634		$ 84,173

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