Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Summary of the allowance for loan losses
Balance at beginning of period	$ 12,477	$ 11,652
Additions:
Provision for loan losses	3,300	150
Deductions:
Loans charged off	134	197
Less recoveries on loans	(50)	(240)
Net loan charge-offs (recoveries)	84	(43)
Balance at end of period	15,693	11,845
Commercial, financial, and agricultural
Summary of the allowance for loan losses
Balance at beginning of period	2,918	3,237
Additions:
Provision for loan losses	721	(60)
Deductions:
Loans charged off	41	53
Less recoveries on loans	(25)	(108)
Net loan charge-offs (recoveries)	16	(55)
Balance at end of period	3,623	3,232
Residential real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	64	140
Additions:
Provision for loan losses	53	(66)
Deductions:
Loans charged off	0
Less recoveries on loans	0
Net loan charge-offs (recoveries)	0
Balance at end of period	117	74
Residential real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	2,118	2,071
Additions:
Provision for loan losses	255	(196)
Deductions:
Loans charged off	19	84
Less recoveries on loans	(9)	(99)
Net loan charge-offs (recoveries)	10	(15)
Balance at end of period	2,363	1,890
Commercial real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	369	757
Additions:
Provision for loan losses	253	(119)
Deductions:
Loans charged off	0
Less recoveries on loans	0
Net loan charge-offs (recoveries)	0
Balance at end of period	622	638
Commercial real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	6,547	4,914
Additions:
Provision for loan losses	2,087	617
Deductions:
Loans charged off	22	8
Less recoveries on loans	(2)
Net loan charge-offs (recoveries)	20	8
Balance at end of period	8,614	5,523
Installment and other consumer
Summary of the allowance for loan losses
Balance at beginning of period	381	334
Additions:
Provision for loan losses	8	18
Deductions:
Loans charged off	52	52
Less recoveries on loans	(14)	(33)
Net loan charge-offs (recoveries)	38	19
Balance at end of period	351	333
Unallocated
Summary of the allowance for loan losses
Balance at beginning of period	80	199
Additions:
Provision for loan losses	(77)	(44)
Deductions:
Loans charged off	0
Less recoveries on loans	0
Net loan charge-offs (recoveries)	0
Balance at end of period	$ 3	$ 155