Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Interest-earning deposits with banks	$ 17,407	$ 97,918
Debt Securities, Available-for-sale	3,167,448	2,737,751
Equity Securities at fair value	0	5,080
Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	260,180	244,615
Interest-earning deposits with banks	17,407	97,918
Debt Securities, Available-for-sale	3,167,448	2,737,751
Equity Securities at fair value		5,080
FHLB stock	25,960	10,440
Loans held for sale	3,849	5,766
Loans	8,316,946	8,055,817
Interest rate contracts	7,033	6,707
Liabilities
Time Deposits	407,659	483,095
FHLB Advances	400,085	12,281
Repurchase agreements	61,094	79,070
Interest rate contracts	7,033	6,714
Subordinated Debt Obligations, Fair Value Disclosure	34,897	35,895
Other Liabilities, Fair Value Disclosure		8,248
Reported Value Measurement [Member]
Assets
Cash and due from banks	260,180	244,615
Interest-earning deposits with banks	17,407	97,918
Debt Securities, Available-for-sale	3,167,448	2,737,751
Equity Securities at fair value		5,080
FHLB stock	25,960	10,440
Loans held for sale	3,849	5,766
Loans	8,308,142	8,283,011
Interest rate contracts	7,033	6,707
Liabilities
Time Deposits	414,443	490,288
FHLB Advances	399,523	11,579
Repurchase agreements	61,094	79,059
Interest rate contracts	7,033	6,714
Subordinated Debt Obligations, Fair Value Disclosure	35,462	35,647
Other Liabilities, Fair Value Disclosure		8,248
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	260,180	244,615
Interest-earning deposits with banks	17,407	97,918
Debt Securities, Available-for-sale	248	248
Equity Securities at fair value		5,080
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
Interest rate contracts	0	0
Liabilities
Time Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	0	0
Subordinated Debt Obligations, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure		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	3,167,200	2,737,503
Equity Securities at fair value		0
FHLB stock	25,960	10,440
Loans held for sale	3,849	5,766
Loans	0	0
Interest rate contracts	7,033	6,707
Liabilities
Time Deposits	407,659	483,095
FHLB Advances	400,085	12,281
Repurchase agreements	61,094	79,070
Interest rate contracts	7,033	6,714
Subordinated Debt Obligations, Fair Value Disclosure	34,897	35,895
Other Liabilities, Fair Value Disclosure		8,248
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	0	0
Equity Securities at fair value		0
FHLB stock	0	0
Loans held for sale	0	0
Loans	8,316,946	8,055,817
Interest rate contracts	0	0
Liabilities
Time Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	0	0
Subordinated Debt Obligations, Fair Value Disclosure	$ 0	0
Other Liabilities, Fair Value Disclosure		$ 0