Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Interest-earning deposits with banks	$ 25,357	$ 24,132
Debt securities available for sale at fair value	3,553,128	3,746,142
Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	190,399	223,541
Interest-earning deposits with banks	25,357	24,132
Debt securities available for sale at fair value	3,553,128	3,746,142
FHLB stock	38,280	48,120
Loans held for sale	9,701	17,718
Loans	8,998,063	8,883,865
Interest rate contracts	49,775	19,144
Interest Rate Cash Flow Hedge Asset at Fair Value	37,209	14,727
Liabilities
Deposits	353,578	397,736
FHLB advances and FRB borrowings	714,022
FHLB advances		952,762
Repurchase agreements	29,252	64,437
Subordinated Debt Obligations, Fair Value Disclosure	35,309	35,491
Revolving line of credit	5,005
Interest rate contracts	49,777	19,145
Reported Value Measurement [Member]
Assets
Cash and due from banks	190,399	223,541
Interest-earning deposits with banks	25,357	24,132
Debt securities available for sale at fair value	3,553,128	3,746,142
FHLB stock	38,280	48,120
Loans held for sale	9,701	17,718
Loans	8,811,247	8,659,497
Interest rate contracts	49,775	19,144
Interest Rate Cash Flow Hedge Asset at Fair Value	37,209	14,727
Liabilities
Deposits	353,536	400,070
FHLB advances and FRB borrowings	712,455
FHLB advances		953,469
Repurchase agreements	29,252	64,437
Subordinated Debt Obligations, Fair Value Disclosure	35,231	35,277
Revolving line of credit	5,000
Interest rate contracts	49,777	19,145
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	190,399	223,541
Interest-earning deposits with banks	25,357	24,132
Debt securities available for sale at fair value	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
Interest rate contracts	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	0	0
Liabilities
Deposits	0	0
FHLB advances and FRB borrowings	0
FHLB advances		0
Repurchase agreements	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Revolving line of credit	0
Interest rate contracts	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Debt securities available for sale at fair value	3,553,128	3,746,142
FHLB stock	38,280	48,120
Loans held for sale	9,701	17,718
Loans	0	0
Interest rate contracts	49,775	19,144
Interest Rate Cash Flow Hedge Asset at Fair Value	37,209	14,727
Liabilities
Deposits	353,578	397,736
FHLB advances and FRB borrowings	714,022
FHLB advances		952,762
Repurchase agreements	29,252	64,437
Subordinated Debt Obligations, Fair Value Disclosure	35,309	35,491
Revolving line of credit	5,005
Interest rate contracts	49,777	19,145
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Debt securities available for sale at fair value	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	8,998,063	8,883,865
Interest rate contracts	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value	0	0
Liabilities
Deposits	0	0
FHLB advances and FRB borrowings	0
FHLB advances		0
Repurchase agreements	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Revolving line of credit	0
Interest rate contracts	$ 0	$ 0