Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	$ 217,207		$ 292,598
Interest-Rate Deposits with Other Banks	202,305		175,336
Loans Held-for-sale	85,477	[1]	47,009	[1]
Securities Held-to-maturity	454		6,669
Securities Available-for-sale	2,789,684	[1]	2,673,298	[1]
Loans, net of unearned income	11,933,001	[1]	11,968,970	[1]
Accrued Interest Receivable	49,784		51,098
Other Financial Assets	151,274	[1]	320,858	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,022,312		8,511,789
Time Deposit Liabilities, Fair Value Disclosure	3,578,998		4,013,950
Short-term borrowings	486,971		597,033
Accrued interest payable	21,818		25,686
Other Financial Liabilities	84,053	[1]	75,151	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	908,623		1,040,149
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	217,207		292,598
Interest-Rate Deposits with Other Banks	202,305		175,336
Loans Held-for-sale	85,477	[1]	47,009	[1]
Securities Held-to-maturity	487		6,699
Securities Available-for-sale	2,789,684	[1]	2,673,298	[1]
Loans, net of unearned income	11,886,084	[1]	11,992,586	[1]
Accrued Interest Receivable	49,784		51,098
Other Financial Assets	151,274	[1]	320,858	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,022,312		8,511,789
Time Deposit Liabilities, Fair Value Disclosure	3,611,952		4,056,247
Short-term borrowings	486,971		597,033
Accrued interest payable	21,818		25,686
Other Financial Liabilities	84,053	[1]	75,151	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	$ 871,236		$ 982,010

[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.