Loans - Nonperforming Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 6,032	$ 1,283
Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	3,521	11
Commercial real estate
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	144	277
Home equity
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,367	995
Nonperforming
Summary of nonperforming loans
Total nonaccrual loans	54,305	44,334
Other real estate owned and repossessed assets	10,605	17,187
Total nonperforming assets	64,910	61,521
Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	15,648	13,178
Nonperforming | Commercial real estate
Summary of nonperforming loans
Total nonaccrual loans	25,150	19,877
Nonperforming | Real estate construction and land development
Summary of nonperforming loans
Total nonaccrual loans	78	80
Nonperforming | Residential mortgage
Summary of nonperforming loans
Total nonaccrual loans	8,646	6,969
Nonperforming | Consumer installment
Summary of nonperforming loans
Total nonaccrual loans	875	879
Nonperforming | Home equity
Summary of nonperforming loans
Total nonaccrual loans	$ 3,908	$ 3,351