Loans, Allowance for Credit Losses and Impaired Loans - Loan by Risk Rating (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Loans by risk rating
Loans and leases receivable, gross	$ 1,015,189	$ 993,988
Non-Accrual	5,311	4,541
TDRs	$ 10,913	$ 10,295
Number of TDR accounts | loan	30	33
Performing
Loans by risk rating
TDRs	$ 8,250	$ 8,427
Non-performing
Loans by risk rating
TDRs	$ 2,663	$ 1,868
Number of TDR accounts | loan	6	7
TDRS on Non-accrual	$ 2,648	$ 1,868
Past Due 30-89 Days | Non-performing
Loans by risk rating
TDRs	15
Excellent
Loans by risk rating
Loans and leases receivable, gross	6,548	6,605
Superior
Loans by risk rating
Loans and leases receivable, gross	5,907	5,732
Good
Loans by risk rating
Loans and leases receivable, gross	973,843	954,986
Fair
Loans by risk rating
Loans and leases receivable, gross	19,538	16,414
Substandard
Loans by risk rating
Loans and leases receivable, gross	9,353	10,251
Real Estate Mortgage | Construction and Land Development
Loans by risk rating
Loans and leases receivable, gross	90,494	84,751
Non-Accrual	177	177
Real Estate Mortgage | Construction and Land Development | Good
Loans by risk rating
Loans and leases receivable, gross	89,498	83,773
Real Estate Mortgage | Construction and Land Development | Fair
Loans by risk rating
Loans and leases receivable, gross	819	801
Real Estate Mortgage | Construction and Land Development | Substandard
Loans by risk rating
Loans and leases receivable, gross	177	177
Real Estate Mortgage | Residential Real Estate
Loans by risk rating
Loans and leases receivable, gross	206,481	209,286
Non-Accrual	1,508	1,620
TDRs	$ 2,269	$ 2,323
Number of TDR accounts | loan	11	12
Real Estate Mortgage | Residential Real Estate | Performing
Loans by risk rating
TDRs	$ 1,388	$ 1,419
Real Estate Mortgage | Residential Real Estate | Non-performing
Loans by risk rating
TDRs	$ 881	$ 904
Number of TDR accounts | loan	3	3
TDRS on Non-accrual	$ 866	$ 904
Real Estate Mortgage | Residential Real Estate | Past Due 30-89 Days | Non-performing
Loans by risk rating
TDRs	15
Real Estate Mortgage | Residential Real Estate | Superior
Loans by risk rating
Loans and leases receivable, gross	134	139
Real Estate Mortgage | Residential Real Estate | Good
Loans by risk rating
Loans and leases receivable, gross	199,142	202,690
Real Estate Mortgage | Residential Real Estate | Fair
Loans by risk rating
Loans and leases receivable, gross	4,207	3,321
Real Estate Mortgage | Residential Real Estate | Substandard
Loans by risk rating
Loans and leases receivable, gross	2,998	3,136
Real Estate Mortgage | Nonresidential
Loans by risk rating
Loans and leases receivable, gross	555,260	544,551
Non-Accrual	2,346	2,608
TDRs	$ 7,437	$ 7,934
Number of TDR accounts | loan	18	20
Real Estate Mortgage | Nonresidential | Performing
Loans by risk rating
TDRs	$ 6,862	$ 7,008
Real Estate Mortgage | Nonresidential | Non-performing
Loans by risk rating
TDRs	$ 575	$ 926
Number of TDR accounts | loan	2	3
TDRS on Non-accrual	$ 575	$ 926
Real Estate Mortgage | Nonresidential | Excellent
Loans by risk rating
Loans and leases receivable, gross	397	405
Real Estate Mortgage | Nonresidential | Superior
Loans by risk rating
Loans and leases receivable, gross	3,580	3,652
Real Estate Mortgage | Nonresidential | Good
Loans by risk rating
Loans and leases receivable, gross	534,658	525,465
Real Estate Mortgage | Nonresidential | Fair
Loans by risk rating
Loans and leases receivable, gross	12,003	9,739
Real Estate Mortgage | Nonresidential | Substandard
Loans by risk rating
Loans and leases receivable, gross	4,622	5,290
Real Estate Mortgage | Home Equity Loans
Loans by risk rating
Loans and leases receivable, gross	37,429	37,714
Non-Accrual		5
Real Estate Mortgage | Home Equity Loans | Superior
Loans by risk rating
Loans and leases receivable, gross	122	122
Real Estate Mortgage | Home Equity Loans | Good
Loans by risk rating
Loans and leases receivable, gross	37,243	37,528
Real Estate Mortgage | Home Equity Loans | Fair
Loans by risk rating
Loans and leases receivable, gross	64	64
Commercial
Loans by risk rating
Loans and leases receivable, gross	119,571	111,997
Non-Accrual	1,280	131
TDRs	$ 1,207	$ 38
Number of TDR accounts | loan	1	1
Commercial | Non-performing
Loans by risk rating
TDRs	$ 1,207	$ 38
Number of TDR accounts | loan	1	1
TDRS on Non-accrual	$ 1,207	$ 38
Commercial | Excellent
Loans by risk rating
Loans and leases receivable, gross	6,044	6,089
Commercial | Superior
Loans by risk rating
Loans and leases receivable, gross	2,071	1,818
Commercial | Good
Loans by risk rating
Loans and leases receivable, gross	107,471	99,973
Commercial | Fair
Loans by risk rating
Loans and leases receivable, gross	2,429	2,469
Commercial | Substandard
Loans by risk rating
Loans and leases receivable, gross	1,556	1,648
Consumer and Other
Loans by risk rating
Loans and leases receivable, gross	5,954	5,689
Consumer and Other | Excellent
Loans by risk rating
Loans and leases receivable, gross	107	111
Consumer and Other | Superior
Loans by risk rating
Loans and leases receivable, gross		1
Consumer and Other | Good
Loans by risk rating
Loans and leases receivable, gross	5,831	5,557
Consumer and Other | Fair
Loans by risk rating
Loans and leases receivable, gross	$ 16	$ 20