Loans - Nonperforming Loans (Details) - Nonperforming - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Summary of nonperforming loans
Total nonaccrual loans	$ 89,324	$ 85,433
Other real estate owned and repossessed assets	9,106	6,256
Total nonperforming assets	98,430	91,689
Commercial
Summary of nonperforming loans
Total nonaccrual loans	33,715	30,139
Total commercial real estate
Summary of nonperforming loans
Total nonaccrual loans	39,817	42,414
Real estate construction and land development
Summary of nonperforming loans
Total nonaccrual loans	3,663	12
Residential mortgage
Summary of nonperforming loans
Total nonaccrual loans	7,665	7,988
Consumer installment
Summary of nonperforming loans
Total nonaccrual loans	1,191	1,276
Home equity
Summary of nonperforming loans
Total nonaccrual loans	3,273	3,604
Owner-occupied | Commercial
Summary of nonperforming loans
Total nonaccrual loans	18,234	16,056
Non-owner occupied | Commercial
Summary of nonperforming loans
Total nonaccrual loans	19,430	23,021
Vacant land | Commercial
Summary of nonperforming loans
Total nonaccrual loans	$ 2,153	$ 3,337