Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Held to maturity investment securities	$ 603,607	$ 611,419
Estimated Fair Value	2,159,806	2,080,294
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	441,388	445,687
FRB and FHLB stock	85,533	79,283
Loans held for sale	27,768	27,099
Held to maturity investment securities	588,443	606,679
Estimated Fair Value	2,159,806	2,080,294
Net Loans	16,100,524	16,005,263
Accrued interest receivable	62,207	58,879
Other financial assets	258,146	235,782
Demand and savings deposits	13,369,831	13,478,016
Brokered deposits	251,395	176,239
Time deposits	2,756,752	2,721,904
Short-term borrowings	829,016	754,777
Accrued interest payable	11,219	10,529
Other financial liabilities	213,443	218,061
FHLB advances and long-term debt	1,065,312	992,279
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	441,388	445,687
FRB and FHLB stock	85,533	79,283
Loans held for sale	27,768	27,099
Held to maturity investment securities	603,607	611,419
Estimated Fair Value	2,159,806	2,080,294
Net Loans	15,747,820	15,446,895
Accrued interest receivable	62,207	58,879
Other financial assets	258,146	235,782
Demand and savings deposits	13,369,831	13,478,016
Brokered deposits	251,395	176,239
Time deposits	2,752,582	2,712,296
Short-term borrowings	829,016	754,777
Accrued interest payable	11,219	10,529
Other financial liabilities	213,443	218,061
FHLB advances and long-term debt	1,051,696	970,985
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	441,388	445,687
FRB and FHLB stock	0	0
Loans held for sale	0	0
Held to maturity investment securities	603,607	611,419
Estimated Fair Value	0	0
Net Loans	0	0
Accrued interest receivable	62,207	58,879
Other financial assets	128,931	124,138
Demand and savings deposits	13,369,831	13,478,016
Brokered deposits	211,395	176,239
Time deposits	0	0
Short-term borrowings	829,016	754,777
Accrued interest payable	11,219	10,529
Other financial liabilities	155,095	161,003
FHLB advances and long-term debt	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	0	0
FRB and FHLB stock	85,533	79,283
Loans held for sale	27,768	27,099
Held to maturity investment securities	0	0
Estimated Fair Value	2,053,796	1,974,025
Net Loans	0	0
Accrued interest receivable	0	0
Other financial assets	81,698	62,552
Demand and savings deposits	0	0
Brokered deposits	40,000	0
Time deposits	2,752,582	2,712,296
Short-term borrowings	0	0
Accrued interest payable	0	0
Other financial liabilities	50,085	48,185
FHLB advances and long-term debt	1,051,696	970,985
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	0	0
FRB and FHLB stock	0	0
Loans held for sale	0	0
Held to maturity investment securities	0	0
Estimated Fair Value	106,010	106,269
Net Loans	15,747,820	15,446,895
Accrued interest receivable	0	0
Other financial assets	47,517	49,092
Demand and savings deposits	0	0
Brokered deposits	0	0
Time deposits	0	0
Short-term borrowings	0	0
Accrued interest payable	0	0
Other financial liabilities	8,263	8,873
FHLB advances and long-term debt	$ 0	$ 0