Loans - Nonperforming Loans (Details) - USD ($) $ in Thousands	Jun. 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	$ 2,346	$ 1,283
Commercial
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	58	11
Commercial real estate
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	262	277
Home equity
Summary of nonperforming loans
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,026	995
Nonperforming
Summary of nonperforming loans
Total nonaccrual loans	50,894	44,334
Other real estate owned and repossessed assets	14,582	17,187
Total nonperforming assets	65,476	61,521
Nonperforming | Commercial
Summary of nonperforming loans
Total nonaccrual loans	18,773	13,178
Nonperforming | Commercial real estate
Summary of nonperforming loans
Total nonaccrual loans	19,723	19,877
Nonperforming | Real estate construction and land development
Summary of nonperforming loans
Total nonaccrual loans	56	80
Nonperforming | Residential mortgage
Summary of nonperforming loans
Total nonaccrual loans	7,714	6,969
Nonperforming | Consumer installment
Summary of nonperforming loans
Total nonaccrual loans	757	879
Nonperforming | Home equity
Summary of nonperforming loans
Total nonaccrual loans	$ 3,871	$ 3,351