Loans - Aging Status of Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule representing the aging status of the recorded investment in loans by classes
Total loans	$ 15,861,903	$ 15,269,779
Originated Portfolio
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	37,241	35,381
Nonaccrual Loans	97,696	85,433
Current	12,736,173	11,723,942
Total loans	12,871,110	11,844,756
Originated Portfolio | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	37,095	33,954
Originated Portfolio | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	146	1,427
Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	19,304	16,835
Nonaccrual Loans	37,762	30,139
Current	3,695,462	3,240,113
Total loans	3,752,528	3,287,087
Originated Portfolio | Commercial | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	19,158	16,835
Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	146	0
Originated Portfolio | Total commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	5,583	7,549
Nonaccrual Loans	43,899	42,414
Current	3,573,006	3,470,194
Total loans	3,622,488	3,520,157
Originated Portfolio | Total commercial real estate | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	5,583	6,610
Originated Portfolio | Total commercial real estate | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	939
Originated Portfolio | Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	538	247
Nonaccrual Loans	3,501	12
Current	667,734	566,467
Total loans	671,773	566,726
Originated Portfolio | Real estate construction and land development | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	538	247
Originated Portfolio | Real estate construction and land development | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	0
Originated Portfolio | Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	6,183	1,688
Nonaccrual Loans	7,636	7,988
Current	2,708,200	2,397,629
Total loans	2,722,019	2,407,305
Originated Portfolio | Residential mortgage | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	6,183	1,688
Originated Portfolio | Residential mortgage | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	0
Originated Portfolio | Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	3,076	4,731
Nonaccrual Loans	1,411	1,276
Current	1,492,980	1,445,345
Total loans	1,497,467	1,451,352
Originated Portfolio | Consumer installment | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	3,076	4,731
Originated Portfolio | Consumer installment | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	0
Originated Portfolio | Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	2,557	4,331
Nonaccrual Loans	3,487	3,604
Current	598,791	604,194
Total loans	604,835	612,129
Originated Portfolio | Home equity | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	2,557	3,843
Originated Portfolio | Home equity | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	488
Owner-occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	3,368	4,709
Nonaccrual Loans	20,814	16,056
Current	1,504,620	1,492,767
Total loans	1,528,802	1,513,532
Owner-occupied | Originated Portfolio | Commercial | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	3,368	4,657
Owner-occupied | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	52
Non-owner occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	1,714	2,680
Nonaccrual Loans	21,639	23,021
Current	2,033,178	1,940,629
Total loans	2,056,531	1,966,330
Non-owner occupied | Originated Portfolio | Commercial | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	1,714	1,793
Non-owner occupied | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	0	887
Vacant land | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	501	160
Nonaccrual Loans	1,446	3,337
Current	35,208	36,798
Total loans	37,155	40,295
Vacant land | Originated Portfolio | Commercial | 30-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	501	160
Vacant land | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Loans Past Due and Still Accruing	$ 0	$ 0