Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	$ 174,479		$ 256,300
Interest-Rate Deposits with Other Banks	97,202		173,257
Loans Held-for-sale	63,045	[1]	67,899	[1]
Securities Held-to-maturity	257		292
Securities Available-for-sale	2,811,847	[1]	2,793,725	[1]
Loans, net of unearned income	12,377,288	[1]	12,146,971	[1]
Accrued Interest Receivable	47,485		45,786
Other Financial Assets	260,857	[1]	201,069	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,120,164		9,100,825
Time Deposit Liabilities, Fair Value Disclosure	3,268,296		3,383,338
Short-term borrowings	1,126,966		868,399
Accrued interest payable	21,393		19,330
Other Financial Liabilities	69,219	[1]	58,255	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	889,211		894,253
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and Cash Equivalents	174,479		256,300
Interest-Rate Deposits with Other Banks	97,202		173,257
Loans Held-for-sale	63,045	[1]	67,899	[1]
Securities Held-to-maturity	279		319
Securities Available-for-sale	2,811,847	[1]	2,793,725	[1]
Loans, net of unearned income	12,345,838	[1]	12,129,971	[1]
Accrued Interest Receivable	47,485		45,786
Other Financial Assets	260,857	[1]	201,069	[1]
Demand and Savings Deposit Liabilities, Fair Value Disclosure	9,120,164		9,100,825
Time Deposit Liabilities, Fair Value Disclosure	3,291,037		3,413,060
Short-term borrowings	1,126,966		868,399
Accrued interest payable	21,393		19,330
Other Financial Liabilities	69,219	[1]	58,255	[1]
Federal Home Loan Bank Advances And Debt Long Term, Fair Value Disclosre	$ 843,624		$ 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.