Loans - Nonperforming Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,662	$ 1,377
Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	472	0
Total commercial real estate
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	477	13
Home equity
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	713	1,364
Nonperforming
Summary of nonperforming loans
Total nonaccrual loans	66,742	63,095
Other real estate owned and repossessed assets	5,828	8,807
Total nonperforming assets	72,570	71,902
Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	20,741	19,691
Nonperforming | Total commercial real estate
Summary of nonperforming loans
Total nonaccrual loans	28,406	29,545
Nonperforming | Real estate construction and land development
Summary of nonperforming loans
Total nonaccrual loans	5,704	77
Nonperforming | Residential mortgage
Summary of nonperforming loans
Total nonaccrual loans	7,974	8,635
Nonperforming | Consumer installment
Summary of nonperforming loans
Total nonaccrual loans	945	842
Nonperforming | Home equity
Summary of nonperforming loans
Total nonaccrual loans	2,972	4,305
Owner-occupied | Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	461	0
Owner-occupied | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	16,103	19,070
Non-owner occupied | Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	13
Non-owner occupied | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	9,168	5,270
Vacant land | Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	16	0
Vacant land | Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	$ 3,135	$ 5,205