Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Federal Home Loan Bank advances and long-term debt	$ 933,981		$ 1,040,149
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	286,875		292,598
Interest-Rate Deposits with Other Banks	106,227		175,336
Loans Held-for-sale	70,128	[1]	47,009	[1]
Securities Held-to-maturity	6,626		6,699
Securities Available-for-sale	3,082,799	[1]	2,673,298	[1]
Loans, net of unearned income	11,793,170	[1]	11,992,586	[1]
Accrued Interest Receivable	51,247		51,098
Other Financial Assets	138,327	[1]	315,952	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	8,464,151		8,511,789
Time Deposit Liabilities, Fair Value Disclosure	3,917,020		4,056,247
Short-term borrowings	964,550		597,033
Accrued interest payable	27,674		25,686
Other Financial Liabilities	122,118	[1]	69,816	[1]
Federal Home Loan Bank advances and long-term debt	876,401		982,010
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	286,875		292,598
Interest-Rate Deposits with Other Banks	106,227		175,336
Loans Held-for-sale	70,128	[1]	47,009	[1]
Securities Held-to-maturity	6,608		6,669
Securities Available-for-sale	3,082,799	[1]	2,673,298	[1]
Loans, net of unearned income	11,957,600	[1]	11,968,970	[1]
Accrued Interest Receivable	51,247		51,098
Other Financial Assets	138,327	[1]	315,952	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	8,464,151		8,511,789
Time Deposit Liabilities, Fair Value Disclosure	3,876,571		4,013,950
Short-term borrowings	964,550		597,033
Accrued interest payable	27,674		25,686
Other Financial Liabilities	122,118	[1]	69,816	[1]
Federal Home Loan Bank advances and long-term debt	$ 933,981		$ 1,040,149

[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.