Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities available for sale	$ 2,484,773	$ 2,323,371
FHLB advances and long-term debt	949,542	1,139,413
Book Value
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Loans held for sale	16,886	17,522
Loans, net of unearned income	13,838,602	13,111,716
Accrued interest receivable	42,767	41,818
Short-term borrowings	497,663	329,719
Accrued interest payable	10,724	18,045
FHLB advances and long-term debt	949,542	1,139,413
Book Value | Cash and due from banks
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	101,120	105,702
Book Value | Interest-bearing Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Interest-bearing deposits with other banks	230,300	358,130
Federal Reserve Bank and FHLB stock	62,216	64,953
Book Value | Available-for-sale Securities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities available for sale	2,484,773	2,323,371
Book Value | Other Assets
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial assets	166,920	169,764
Book Value | Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Demand and savings deposits	11,267,367	10,296,055
Time deposits	2,864,950	3,071,451
Book Value | Other financial liabilities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial liabilities	190,927	172,786
Estimated Fair Value
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Loans held for sale	16,886	17,522
Loans, net of unearned income	13,709,957	13,030,543
Accrued interest receivable	42,767	41,818
Short-term borrowings	497,663	329,719
Accrued interest payable	10,724	18,045
FHLB advances and long-term debt	959,315	1,142,980
Estimated Fair Value | Cash and due from banks
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	101,120	105,702
Estimated Fair Value | Interest-bearing Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Interest-bearing deposits with other banks	230,300	358,130
Federal Reserve Bank and FHLB stock	62,216	64,953
Estimated Fair Value | Available-for-sale Securities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities available for sale	2,484,773	2,323,371
Estimated Fair Value | Other Assets
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial assets	166,920	169,764
Estimated Fair Value | Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Demand and savings deposits	11,267,367	10,296,055
Time deposits	2,862,868	3,069,883
Estimated Fair Value | Other financial liabilities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial liabilities	$ 190,927	$ 172,786