Loans - Aging Status of Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule representing the aging status of the recorded investment in loans by classes
Total loans	$ 13,667,372	$ 12,990,779
90 days or more past due and still accruing	2,346	1,283
Commercial
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	58	11
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	262	277
Home equity
Schedule representing the aging status of the recorded investment in loans by classes
90 days or more past due and still accruing	2,026	995
Originated Portfolio
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	68,611	51,633
Current	8,591,011	7,406,768
Total loans	8,659,622	7,458,401
90 days or more past due and still accruing	2,346	1,283
Originated Portfolio | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	34,446	29,928
Originated Portfolio | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	16,991	8,560
Originated Portfolio | 90 days or more past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	17,174	13,145
Originated Portfolio | Commercial
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	19,590	18,904
Current	2,164,693	1,882,622
Total loans	2,184,283	1,901,526
90 days or more past due and still accruing	58	11
Originated Portfolio | Commercial | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	6,578	10,421
Originated Portfolio | Commercial | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	5,408	4,842
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	7,604	3,641
Originated Portfolio | Commercial real estate
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	33,845	13,305
Current	2,371,927	1,908,494
Total loans	2,405,772	1,921,799
90 days or more past due and still accruing	262	277
Originated Portfolio | Commercial real estate | 30-59 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	21,106	6,551
Originated Portfolio | Commercial real estate | 60-89 days past due
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	7,518	1,589
Originated Portfolio | 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	5,221	5,165
Originated Portfolio | Real estate construction and land development
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	0	3,220
Current	349,395	278,504
Total loans	349,395	281,724
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	2,721
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	499
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	0	0
Originated Portfolio | Residential mortgage
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	4,436	4,961
Current	1,679,114	1,470,381
Total loans	1,683,550	1,475,342
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	411	3,147
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	2,607	62
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	1,418	1,752
Originated Portfolio | Consumer installment
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	3,072	4,904
Current	1,426,016	1,277,684
Total loans	1,429,088	1,282,588
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	2,553	3,991
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	363	675
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	156	238
Originated Portfolio | Home equity
Schedule representing the aging status of the recorded investment in loans by classes
Total past due	7,668	6,339
Current	599,866	589,083
Total loans	607,534	595,422
90 days or more past due and still accruing	2,026	995
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	3,798	3,097
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	1,095	893
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	$ 2,775	$ 2,349