Loans and Allowance for Loan Losses - Loans outstanding by portfolio segment (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Loans and Allowance for Loan Losses
Total loans	$ 1,686,087	$ 1,701,850
Deferred loan fees and costs	1,100	1,700
Pledged
Loans and Allowance for Loan Losses
Total loans	1,100,000	1,100,000
Commercial
Loans and Allowance for Loan Losses
Total loans	951,457	969,634
Consumer
Loans and Allowance for Loan Losses
Total loans	734,630	732,216
Commercial and industrial | Commercial
Loans and Allowance for Loan Losses
Total loans	485,183	510,706
Real estate construction | Commercial
Loans and Allowance for Loan Losses
Total loans	21,674	18,965
Residential | Consumer | Real estate first mortgage
Loans and Allowance for Loan Losses
Total loans	459,763	448,143
Residential | Consumer | Real estate junior lien
Loans and Allowance for Loan Losses
Total loans	182,516	188,855
Commercial real estate | Commercial
Loans and Allowance for Loan Losses
Total loans	444,600	439,963
Other revolving and installment | Consumer
Loans and Allowance for Loan Losses
Total loans	$ 92,351	$ 95,218