Loans and Allowance for Loan Losses - Loans by risk category (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans outstanding by loan portfolio segment and risk category
Loans	$ 2,058,419	$ 1,721,279
Pass
Loans outstanding by loan portfolio segment and risk category
Loans	1,989,780	1,654,719
Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	20,172	12,226
Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	48,467	54,334
Commercial
Loans outstanding by loan portfolio segment and risk category
Loans	1,357,421	1,000,225
Commercial | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	1,293,861	935,719
Commercial | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	16,754	12,226
Commercial | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	46,806	52,280
Commercial | Commercial and industrial
Loans outstanding by loan portfolio segment and risk category
Loans	789,036	479,144
Commercial | Commercial and industrial | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	759,808	448,306
Commercial | Commercial and industrial | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	8,706	9,585
Commercial | Commercial and industrial | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	20,522	21,253
Commercial | Real estate construction
Loans outstanding by loan portfolio segment and risk category
Loans	33,169	26,378
Commercial | Real estate construction | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	32,140	25,119
Commercial | Real estate construction | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	783	282
Commercial | Real estate construction | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	246	977
Commercial | Commercial real estate
Loans outstanding by loan portfolio segment and risk category
Loans	535,216	494,703
Commercial | Commercial real estate | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	501,913	462,294
Commercial | Commercial real estate | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	7,265	2,359
Commercial | Commercial real estate | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	26,038	30,050
Consumer
Loans outstanding by loan portfolio segment and risk category
Loans	700,998	721,054
Consumer | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	695,919	719,000
Consumer | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	3,418
Consumer | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	1,661	2,054
Consumer | Residential | Real estate first mortgage
Loans outstanding by loan portfolio segment and risk category
Loans	469,050	457,155
Consumer | Residential | Real estate first mortgage | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	467,168	456,358
Consumer | Residential | Real estate first mortgage | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	1,413
Consumer | Residential | Real estate first mortgage | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	469	797
Consumer | Residential | Real estate junior lien
Loans outstanding by loan portfolio segment and risk category
Loans	152,487	177,373
Consumer | Residential | Real estate junior lien | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	149,290	176,122
Consumer | Residential | Real estate junior lien | Special Mention
Loans outstanding by loan portfolio segment and risk category
Loans	2,005
Consumer | Residential | Real estate junior lien | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans	1,192	1,251
Consumer | Other revolving and installment
Loans outstanding by loan portfolio segment and risk category
Loans	79,461	86,526
Consumer | Other revolving and installment | Pass
Loans outstanding by loan portfolio segment and risk category
Loans	$ 79,461	86,520
Consumer | Other revolving and installment | Substandard
Loans outstanding by loan portfolio segment and risk category
Loans		$ 6