Fair Value Measurements Details of Book Value and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Held to maturity investment securities	$ 403,957	$ 611,419
Estimated Fair Value	2,315,541	2,080,294
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	598,613	445,687
FRB and FHLB stock	94,557	79,283
Loans held for sale	33,945	27,099
Held to maturity investment securities	390,069	606,679
Estimated Fair Value	2,315,541	2,080,294
Net Loans	16,520,731	16,005,263
Accrued interest receivable	60,447	58,879
Other financial assets	478,924	235,782
Demand and savings deposits	14,105,974	13,478,016
Brokered deposits	256,870	176,239
Time deposits	2,979,873	2,721,904
Short-term borrowings	832,860	754,777
Accrued interest payable	9,622	10,529
Other financial liabilities	288,477	218,061
FHLB advances and long-term debt	726,714	992,279
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, FinancialStatement Captions[Line Items]
Cash and due from banks	598,613	445,687
FRB and FHLB stock	94,557	79,283
Loans held for sale	33,945	27,099
Held to maturity investment securities	403,957	611,419
Estimated Fair Value	2,315,541	2,080,294
Net Loans	16,427,675	15,446,895
Accrued interest receivable	60,447	58,879
Other financial assets	483,536	235,782
Demand and savings deposits	14,105,974	13,478,016
Brokered deposits	257,420	176,239
Time deposits	3,002,796	2,712,296
Short-term borrowings	832,860	754,777
Accrued interest payable	9,622	10,529
Other financial liabilities	288,477	218,061
FHLB advances and long-term debt	723,194	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	598,613	445,687
FRB and FHLB stock	0	0
Loans held for sale	0	0
Held to maturity investment securities	0	0
Estimated Fair Value	0	0
Net Loans	0	0
Accrued interest receivable	60,447	58,879
Other financial assets	236,599	124,138
Demand and savings deposits	14,105,974	13,478,016
Brokered deposits	216,870	176,239
Time deposits	0	0
Short-term borrowings	832,860	754,777
Accrued interest payable	9,622	10,529
Other financial liabilities	176,799	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	94,557	79,283
Loans held for sale	33,945	27,099
Held to maturity investment securities	403,957	611,419
Estimated Fair Value	2,209,873	1,974,025
Net Loans	0	0
Accrued interest receivable	0	0
Other financial assets	195,263	62,552
Demand and savings deposits	0	0
Brokered deposits	40,550	0
Time deposits	3,002,796	2,712,296
Short-term borrowings	0	0
Accrued interest payable	0	0
Other financial liabilities	105,016	48,185
FHLB advances and long-term debt	723,194	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	105,668	106,269
Net Loans	16,427,675	15,446,895
Accrued interest receivable	0	0
Other financial assets	51,674	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	6,662	8,873
FHLB advances and long-term debt	$ 0	$ 0