Loans - Summary of Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Summary of loans under portfolio
Total loans	$ 15,861,903	$ 15,269,779
Deferred income	27,200	19,700
Commercial loan portfolio
Summary of loans under portfolio
Total loans	9,895,855	9,511,867
Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	4,347,885	4,002,568
Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	4,847,200	4,912,087
Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	700,770	597,212
Consumer loan portfolio
Summary of loans under portfolio
Total loans	5,966,048	5,757,912
Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	3,666,613	3,458,666
Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,552,835	1,521,074
Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	746,600	778,172
Originated
Summary of loans under portfolio
Total loans	12,871,110	11,844,756
Originated | Commercial
Summary of loans under portfolio
Total loans	3,752,528	3,287,087
Originated | Total commercial real estate
Summary of loans under portfolio
Total loans	3,622,488	3,520,157
Originated | Real estate construction and land development
Summary of loans under portfolio
Total loans	671,773	566,726
Originated | Residential mortgage
Summary of loans under portfolio
Total loans	2,722,019	2,407,305
Originated | Consumer installment
Summary of loans under portfolio
Total loans	1,497,467	1,451,352
Originated | Home equity
Summary of loans under portfolio
Total loans	604,835	612,129
Originated | Commercial loan portfolio
Summary of loans under portfolio
Total loans	8,046,789	7,373,970
Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	3,752,528	3,287,087
Originated | Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	3,622,488	3,520,157
Originated | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	671,773	566,726
Originated | Consumer loan portfolio
Summary of loans under portfolio
Total loans	4,824,321	4,470,786
Originated | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	2,722,019	2,407,305
Originated | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	1,497,467	1,451,352
Originated | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	604,835	612,129
Acquired
Summary of loans under portfolio
Total loans	2,990,793	3,425,023
Acquired | Commercial loan portfolio
Summary of loans under portfolio
Total loans	1,849,066	2,137,897
Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	595,357	715,481
Acquired | Commercial loan portfolio | Total commercial real estate
Summary of loans under portfolio
Total loans	1,224,712	1,391,930
Acquired | Commercial loan portfolio | Real estate construction and land development
Summary of loans under portfolio
Total loans	28,997	30,486
Acquired | Consumer loan portfolio
Summary of loans under portfolio
Total loans	1,141,727	1,287,126
Acquired | Consumer loan portfolio | Residential mortgage
Summary of loans under portfolio
Total loans	944,594	1,051,361
Acquired | Consumer loan portfolio | Consumer installment
Summary of loans under portfolio
Total loans	55,368	69,722
Acquired | Consumer loan portfolio | Home equity
Summary of loans under portfolio
Total loans	141,765	166,043
Owner-occupied | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,024,561	2,059,557
Owner-occupied | Originated | Commercial
Summary of loans under portfolio
Total loans	1,528,802	1,513,532
Owner-occupied | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	1,528,802	1,513,532
Owner-occupied | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	495,759	546,025
Non-owner occupied | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,772,677	2,785,020
Non-owner occupied | Originated | Commercial
Summary of loans under portfolio
Total loans	2,056,531	1,966,330
Non-owner occupied | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	2,056,531	1,966,330
Non-owner occupied | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	716,146	818,690
Vacant land | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	49,962	67,510
Vacant land | Originated | Commercial
Summary of loans under portfolio
Total loans	37,155	40,295
Vacant land | Originated | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	37,155	40,295
Vacant land | Acquired | Commercial loan portfolio | Commercial
Summary of loans under portfolio
Total loans	$ 12,807	$ 27,215