Fair Value of Financial Instruments - Carrying values and fair values of financial instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial Assets:
Federal funds sold	$ 6,380	$ 0
Marketable equity securities	2,203	2,118
Available for sale securities	90,563	82,439
Held to maturity securities	16,138	16,308
Derivative asset	5,512	2,363
Financial Liabilities:
Derivative liability	33,205	13,032
Level 1
Financial Assets:
Cash and due from banks	333,103	78,051
Federal funds sold	6,380
Marketable equity securities	2,203	2,118
Available for sale securities	10,189	10,031
Held to maturity securities	0	0
Loans receivable, net	0	0
Accrued interest receivable	0	0
FHLB stock	0	0
Servicing asset, net of valuation allowance	0	0
Derivative asset	0	0
Financial Liabilities:
Noninterest bearing deposits	0	0
NOW and money market	0	0
Savings	0	0
Time deposits	0	0
Accrued interest payable	0	0
Advances from the FHLB	0	0
Subordinated debentures	0	0
Servicing liability	0	0
Derivative liability	0	0
Level 2
Financial Assets:
Cash and due from banks	0	0
Federal funds sold	0
Marketable equity securities	0	0
Available for sale securities	80,374	72,408
Held to maturity securities	75	85
Loans receivable, net	0	0
Accrued interest receivable	7,294	5,959
FHLB stock	7,860	7,475
Servicing asset, net of valuation allowance	0	0
Derivative asset	5,474	2,266
Financial Liabilities:
Noninterest bearing deposits	234,848	191,518
NOW and money market	651,877	489,515
Savings	164,590	183,729
Time deposits	0	0
Accrued interest payable	1,885	2,142
Advances from the FHLB	0	0
Subordinated debentures	0	0
Servicing liability	0	0
Derivative liability	32,565	12,957
Level 3
Financial Assets:
Cash and due from banks	0	0
Federal funds sold	0
Marketable equity securities	0	0
Available for sale securities	0	0
Held to maturity securities	19,741	18,222
Loans receivable, net	1,611,664	1,589,732
Accrued interest receivable	0	0
FHLB stock	0	0
Servicing asset, net of valuation allowance	647	978
Derivative asset	0	0
Financial Liabilities:
Noninterest bearing deposits	0	0
NOW and money market	0	0
Savings	0	0
Time deposits	722,506	632,436
Accrued interest payable	0	0
Advances from the FHLB	174,998	150,006
Subordinated debentures	25,231	25,530
Servicing liability	29	63
Derivative liability	0	0
Carrying Value
Financial Assets:
Cash and due from banks	333,103	78,051
Federal funds sold	6,380
Marketable equity securities	2,203	2,118
Available for sale securities	90,563	82,439
Held to maturity securities	16,138	16,308
Loans receivable, net	1,600,776	1,588,840
Accrued interest receivable	7,294	5,959
FHLB stock	7,860	7,475
Servicing asset, net of valuation allowance	647	978
Derivative asset	5,474	2,266
Financial Liabilities:
Noninterest bearing deposits	234,848	191,518
NOW and money market	651,877	489,515
Savings	164,590	183,729
Time deposits	716,213	627,141
Accrued interest payable	1,885	2,142
Advances from the FHLB	175,000	150,000
Subordinated debentures	25,245	25,207
Servicing liability	29	63
Derivative liability	32,565	12,957
Fair Value
Financial Assets:
Cash and due from banks	333,103	78,051
Federal funds sold	6,380
Marketable equity securities	2,203	2,118
Available for sale securities	90,563	82,439
Held to maturity securities	19,816	18,307
Loans receivable, net	1,611,664	1,589,732
Accrued interest receivable	7,294	5,959
FHLB stock	7,860	7,475
Servicing asset, net of valuation allowance	647	978
Derivative asset	5,474	2,266
Financial Liabilities:
Noninterest bearing deposits	234,848	191,518
NOW and money market	651,877	489,515
Savings	164,590	183,729
Time deposits	722,506	632,436
Accrued interest payable	1,885	2,142
Advances from the FHLB	174,998	150,006
Subordinated debentures	25,231	25,530
Servicing liability	29	63
Derivative liability	$ 32,565	$ 12,957