Loans - Aging Status of Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule representing the aging status of the recorded investment in loans by classes
Total loans	$ 14,579,693	$ 14,155,267
90 days or more past due and still accruing	1,662	1,377
Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	472	0
Total commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	477	13
Home equity
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	713	1,364
Originated Portfolio
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	80,808	58,857
Current	10,615,725	9,688,572
Total loans	10,696,533	9,747,429
90 days or more past due and still accruing	1,662	1,377
Originated Portfolio | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	36,410	31,724
Originated Portfolio | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	11,651	8,486
Originated Portfolio | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	32,747	18,647
Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	28,344	27,166
Current	2,725,260	2,380,440
Total loans	2,753,604	2,407,606
90 days or more past due and still accruing	472	0
Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	12,421	13,906
Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,294	3,766
Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	11,629	9,494
Originated Portfolio | Total commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	30,390	16,815
Current	3,087,939	2,734,610
Total loans	3,118,329	2,751,425
90 days or more past due and still accruing	477	13
Originated Portfolio | Total commercial real estate | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	16,842	9,380
Originated Portfolio | Total commercial real estate | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,130	1,562
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
Total past due	10,418	5,873
Originated Portfolio | Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,565	0
Current	544,882	498,155
Total loans	550,447	498,155
90 days or more past due and still accruing	0	0
Originated Portfolio | Real estate construction and land development | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	0
Originated Portfolio | Real estate construction and land development | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	0
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
Total past due	5,565	0
Originated Portfolio | Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	6,153	5,068
Current	2,156,072	1,962,789
Total loans	2,162,225	1,967,857
90 days or more past due and still accruing	0	0
Originated Portfolio | Residential mortgage | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	440	2,795
Originated Portfolio | Residential mortgage | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,814	1,415
Originated Portfolio | Residential mortgage | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,899	858
Originated Portfolio | Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,379	3,992
Current	1,498,521	1,506,548
Total loans	1,501,900	1,510,540
90 days or more past due and still accruing	0	0
Originated Portfolio | Consumer installment | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,777	3,324
Originated Portfolio | Consumer installment | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	385	442
Originated Portfolio | Consumer installment | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	217	226
Originated Portfolio | Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	6,977	5,816
Current	603,051	606,030
Total loans	610,028	611,846
90 days or more past due and still accruing	713	1,364
Originated Portfolio | Home equity | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,930	2,319
Originated Portfolio | Home equity | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,028	1,301
Originated Portfolio | Home equity | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,019	2,196
Owner-occupied | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	461	0
Owner-occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	27,037	13,977
Current	1,225,346	1,171,637
Total loans	1,252,383	1,185,614
90 days or more past due and still accruing	461	0
Owner-occupied | Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	15,233	7,644
Owner-occupied | Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	2,771	1,306
Owner-occupied | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	9,033	5,027
Non-owner occupied | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	0	13
Non-owner occupied | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,070	2,574
Current	1,816,465	1,516,213
Total loans	1,819,535	1,518,787
90 days or more past due and still accruing	0	13
Non-owner occupied | Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	1,551	1,653
Non-owner occupied | Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	359	228
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
Total past due	1,160	693
Vacant land | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	16	0
Vacant land | Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	283	264
Current	46,128	46,760
Total loans	46,411	47,024
90 days or more past due and still accruing	16	0
Vacant land | Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	58	83
Vacant land | Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	28
Vacant land | Originated Portfolio | Commercial | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	$ 225	$ 153