Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities available for sale	$ 2,559,227	$ 2,484,773
FHLB advances and long-term debt	929,403	949,542
Book Value
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Loans held for sale	28,697	16,886
Loans, net of unearned income	14,530,593	13,669,548
Accrued interest receivable	46,294	42,767
Short-term borrowings	541,317	497,663
Accrued interest payable	9,632	10,724
FHLB advances and long-term debt	929,403	949,542
Book Value | Cash and due from banks
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	118,763	101,120
Book Value | Interest-bearing Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Interest-bearing deposits with other banks	233,763	230,300
Federal Reserve Bank and FHLB stock	57,489	62,216
Book Value | Available-for-sale Securities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities available for sale	2,559,227	2,484,773
Book Value | Other Assets
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial assets	206,132	166,920
Book Value | Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Demand and savings deposits	12,259,622	11,267,367
Time deposits	2,753,242	2,864,950
Book Value | Other financial liabilities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial liabilities	216,080	190,927
Estimated Fair Value
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Loans held for sale	28,697	16,886
Loans, net of unearned income	14,387,454	13,540,903
Accrued interest receivable	46,294	42,767
Short-term borrowings	541,317	497,663
Accrued interest payable	9,632	10,724
FHLB advances and long-term debt	928,167	959,315
Estimated Fair Value | Cash and due from banks
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	118,763	101,120
Estimated Fair Value | Interest-bearing Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Interest-bearing deposits with other banks	233,763	230,300
Federal Reserve Bank and FHLB stock	57,489	62,216
Estimated Fair Value | Available-for-sale Securities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Securities available for sale	2,559,227	2,484,773
Estimated Fair Value | Other Assets
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial assets	206,132	166,920
Estimated Fair Value | Deposits
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Demand and savings deposits	12,259,622	11,267,367
Time deposits	2,769,757	2,862,868
Estimated Fair Value | Other financial liabilities
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Other financial liabilities	$ 216,080	$ 190,927