Loans and Allowance for Loan Losses - Loans by risk category (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Loans outstanding by loan portfolio segment and risk category
Loans	$ 1,721,279	$ 1,701,850
Pass
Loans outstanding by loan portfolio segment and risk category
Loans	1,654,719	1,614,365
Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	12,226	18,359
Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	54,334	67,563
Doubtful
Loans outstanding by loan portfolio segment and risk category
Loans		1,563
Commercial
Loans outstanding by loan portfolio segment and risk category
Loans	1,000,225	969,634
Commercial | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	935,719	884,653
Commercial | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	12,226	18,359
Commercial | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	52,280	65,059
Commercial | Doubtful
Loans outstanding by loan portfolio segment and risk category
Loans		1,563
Commercial | Commercial and industrial
Loans outstanding by loan portfolio segment and risk category
Loans	479,144	510,706
Commercial | Commercial and industrial | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	448,306	459,565
Commercial | Commercial and industrial | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	9,585	12,055
Commercial | Commercial and industrial | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	21,253	37,523
Commercial | Commercial and industrial | Doubtful
Loans outstanding by loan portfolio segment and risk category
Loans		1,563
Commercial | Real estate construction
Loans outstanding by loan portfolio segment and risk category
Loans	26,378	18,965
Commercial | Real estate construction | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	25,119	17,910
Commercial | Real estate construction | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	282
Commercial | Real estate construction | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	977	1,055
Commercial | Commercial real estate
Loans outstanding by loan portfolio segment and risk category
Loans	494,703	439,963
Commercial | Commercial real estate | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	462,294	407,178
Commercial | Commercial real estate | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	2,359	6,304
Commercial | Commercial real estate | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	30,050	26,481
Consumer
Loans outstanding by loan portfolio segment and risk category
Loans	721,054	732,216
Consumer | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	719,000	729,712
Consumer | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	2,054	2,504
Consumer | Residential | Real estate first mortgage
Loans outstanding by loan portfolio segment and risk category
Loans	457,155	448,143
Consumer | Residential | Real estate first mortgage | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	456,358	448,124
Consumer | Residential | Real estate first mortgage | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	797	19
Consumer | Residential | Real estate junior lien
Loans outstanding by loan portfolio segment and risk category
Loans	177,373	188,855
Consumer | Residential | Real estate junior lien | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	176,122	186,370
Consumer | Residential | Real estate junior lien | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	1,251	2,485
Consumer | Other revolving and installment
Loans outstanding by loan portfolio segment and risk category
Loans	86,526	95,218
Consumer | Other revolving and installment | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	86,520	$ 95,218
Consumer | Other revolving and installment | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	$ 6