Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	$ 262,938		$ 256,300
Interest-Rate Deposits with Other Banks	221,064		173,257
Loans Held-for-sale	39,273	[1]	67,899	[1]
Securities Held-to-maturity	206		292
Securities Available-for-sale	2,686,443	[1]	2,793,725	[1]
Loans, net of unearned income	12,780,899	[1]	12,146,971	[1]
Accrued Interest Receivable	44,715		45,786
Other Financial Assets	144,367	[1]	201,069	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,696,547		9,100,825
Time Deposit Liabilities, Fair Value Disclosure	3,024,574		3,383,338
Short-term borrowings	1,198,577		868,399
Accrued interest payable	16,657		19,330
Other Financial Liabilities	67,773	[1]	58,255	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	889,122		894,253
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	262,938		256,300
Interest-Rate Deposits with Other Banks	221,064		173,257
Loans Held-for-sale	39,273	[1]	67,899	[1]
Securities Held-to-maturity	224		319
Securities Available-for-sale	2,686,443	[1]	2,793,725	[1]
Loans, net of unearned income	12,730,181	[1]	12,129,971	[1]
Accrued Interest Receivable	44,715		45,786
Other Financial Assets	144,367	[1]	201,069	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,696,547		9,100,825
Time Deposit Liabilities, Fair Value Disclosure	3,040,852		3,413,060
Short-term borrowings	1,198,577		868,399
Accrued interest payable	16,657		19,330
Other Financial Liabilities	67,773	[1]	58,255	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	$ 888,850		$ 853,547

[1] Description of fair value determinations for these financial instruments, or certain financial instruments within these categories, measured at fair value on the Corporation’s consolidated balance sheets, are disclosed above.