Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Held to maturity investment securities	$ 589,728	$ 611,419
Estimated Fair Value	2,285,794	2,080,294
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	498,811	445,687
FRB and FHLB stock	97,248	79,283
Loans held for sale	45,754	27,099
Held to maturity investment securities	567,564	606,679
Estimated Fair Value	2,285,794	2,080,294
Net Loans	16,198,225	16,005,263
Accrued interest receivable	62,984	58,879
Other financial assets	318,776	235,782
Demand and savings deposits	13,249,017	13,478,016
Brokered deposits	246,116	176,239
Time deposits	2,893,762	2,721,904
Short-term borrowings	1,188,390	754,777
Accrued interest payable	9,218	10,529
Other financial liabilities	249,381	218,061
FHLB advances and long-term debt	987,416	992,279
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	498,811	445,687
FRB and FHLB stock	97,248	79,283
Loans held for sale	45,754	27,099
Held to maturity investment securities	589,728	611,419
Estimated Fair Value	2,285,794	2,080,294
Net Loans	16,019,233	15,446,895
Accrued interest receivable	62,984	58,879
Other financial assets	318,776	235,782
Demand and savings deposits	13,249,017	13,478,016
Brokered deposits	246,408	176,239
Time deposits	2,894,290	2,712,296
Short-term borrowings	1,188,390	754,777
Accrued interest payable	9,218	10,529
Other financial liabilities	249,381	218,061
FHLB advances and long-term debt	986,336	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	498,811	445,687
FRB and FHLB stock	0	0
Loans held for sale	0	0
Held to maturity investment securities	589,728	611,419
Estimated Fair Value	0	0
Net Loans	0	0
Accrued interest receivable	62,984	58,879
Other financial assets	132,356	124,138
Demand and savings deposits	13,249,017	13,478,016
Brokered deposits	206,116	176,239
Time deposits	0	0
Short-term borrowings	1,188,390	754,777
Accrued interest payable	9,218	10,529
Other financial liabilities	164,790	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	97,248	79,283
Loans held for sale	45,754	27,099
Held to maturity investment securities	0	0
Estimated Fair Value	2,180,059	1,974,025
Net Loans	0	0
Accrued interest receivable	0	0
Other financial assets	140,353	62,552
Demand and savings deposits	0	0
Brokered deposits	40,292	0
Time deposits	2,894,290	2,712,296
Short-term borrowings	0	0
Accrued interest payable	0	0
Other financial liabilities	77,883	48,185
FHLB advances and long-term debt	986,336	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	105,735	106,269
Net Loans	16,019,233	15,446,895
Accrued interest receivable	0	0
Other financial assets	46,067	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	6,708	8,873
FHLB advances and long-term debt	$ 0	$ 0