Loans (Summary of Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Summary of loans under portfolio
Loans	$ 15,269,779	$ 14,155,267
Deferred costs	19,700	26,100
Commercial Loan Portfolio
Summary of loans under portfolio
Loans	9,511,867	8,460,527
Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	4,002,568	3,385,642
Commercial Loan Portfolio | Commercial real estate:
Summary of loans under portfolio
Loans	4,912,087	4,500,670
Commercial Loan Portfolio | Real estate construction and land development
Summary of loans under portfolio
Loans	597,212	574,215
Consumer Loan Portfolio
Summary of loans under portfolio
Loans	5,757,912	5,694,740
Consumer Loan Portfolio | Residential mortgage
Summary of loans under portfolio
Loans	3,458,666	3,252,487
Consumer Loan Portfolio | Consumer installment
Summary of loans under portfolio
Loans	1,521,074	1,613,008
Consumer Loan Portfolio | Home equity
Summary of loans under portfolio
Loans	778,172	829,245
Originated
Summary of loans under portfolio
Loans	11,844,756	9,747,429
Originated | Commercial
Summary of loans under portfolio
Loans	3,287,087	2,407,606
Originated | Commercial real estate:
Summary of loans under portfolio
Loans	3,520,157	2,751,425
Originated | Real estate construction and land development
Summary of loans under portfolio
Loans	566,726	498,155
Originated | Residential mortgage
Summary of loans under portfolio
Loans	2,407,305	1,967,857
Originated | Consumer installment
Summary of loans under portfolio
Loans	1,451,352	1,510,540
Originated | Home equity
Summary of loans under portfolio
Loans	612,129	611,846
Originated | Commercial Loan Portfolio
Summary of loans under portfolio
Loans	7,373,970	5,657,186
Originated | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	3,287,087	2,407,606
Originated | Commercial Loan Portfolio | Commercial real estate:
Summary of loans under portfolio
Loans	3,520,157	2,751,425
Originated | Commercial Loan Portfolio | Real estate construction and land development
Summary of loans under portfolio
Loans	566,726	498,155
Originated | Consumer Loan Portfolio
Summary of loans under portfolio
Loans	4,470,786	4,090,243
Originated | Consumer Loan Portfolio | Residential mortgage
Summary of loans under portfolio
Loans	2,407,305	1,967,857
Originated | Consumer Loan Portfolio | Consumer installment
Summary of loans under portfolio
Loans	1,451,352	1,510,540
Originated | Consumer Loan Portfolio | Home equity
Summary of loans under portfolio
Loans	612,129	611,846
Acquired
Summary of loans under portfolio
Loans	3,425,023	4,407,838
Acquired | Commercial Loan Portfolio
Summary of loans under portfolio
Loans	2,137,897	2,803,341
Acquired | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	715,481	978,036
Acquired | Commercial Loan Portfolio | Commercial real estate:
Summary of loans under portfolio
Loans	1,391,930	1,749,245
Acquired | Commercial Loan Portfolio | Real estate construction and land development
Summary of loans under portfolio
Loans	30,486	76,060
Acquired | Consumer Loan Portfolio
Summary of loans under portfolio
Loans	1,287,126	1,604,497
Acquired | Consumer Loan Portfolio | Residential mortgage
Summary of loans under portfolio
Loans	1,051,361	1,284,630
Acquired | Consumer Loan Portfolio | Consumer installment
Summary of loans under portfolio
Loans	69,722	102,468
Acquired | Consumer Loan Portfolio | Home equity
Summary of loans under portfolio
Loans	166,043	217,399
Owner-occupied | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	2,059,557	1,813,562
Owner-occupied | Originated | Commercial
Summary of loans under portfolio
Loans	1,513,532	1,185,614
Owner-occupied | Originated | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	1,513,532	1,185,614
Owner-occupied | Acquired | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	546,025	627,948
Non-owner occupied | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	2,785,020	2,606,761
Non-owner occupied | Originated | Commercial
Summary of loans under portfolio
Loans	1,966,330	1,518,787
Non-owner occupied | Originated | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	1,966,330	1,518,787
Non-owner occupied | Acquired | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	818,690	1,087,974
Vacant land | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	67,510	80,347
Vacant land | Originated | Commercial
Summary of loans under portfolio
Loans	40,295	47,024
Vacant land | Originated | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	40,295	47,024
Vacant land | Acquired | Commercial Loan Portfolio | Commercial
Summary of loans under portfolio
Loans	$ 27,215	$ 33,323