Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Summary of the allowance for loan losses
Balance at beginning of period	$ 11,652	$ 10,852
Additions:
Provision for loan losses	150	300
Deductions:
Loans charged off	197	279
Less recoveries on loans	(240)	(74)
Net loan charge-offs (recoveries)	(43)	205
Balance at end of period	11,845	10,947
Commercial, financial, and agricultural
Summary of the allowance for loan losses
Balance at beginning of period	3,237	3,325
Additions:
Provision for loan losses	(60)	33
Deductions:
Loans charged off	53	110
Less recoveries on loans	(108)	(13)
Net loan charge-offs (recoveries)	(55)	97
Balance at end of period	3,232	3,261
Residential real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	140	170
Additions:
Provision for loan losses	(66)	106
Deductions:
Loans charged off	0	48
Less recoveries on loans	0	(12)
Net loan charge-offs (recoveries)	0	36
Balance at end of period	74	240
Residential real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	2,071	1,689
Additions:
Provision for loan losses	(196)	369
Deductions:
Loans charged off	84	20
Less recoveries on loans	(99)	(19)
Net loan charge-offs (recoveries)	(15)	1
Balance at end of period	1,890	2,057
Commercial real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	757	807
Additions:
Provision for loan losses	(119)	118
Deductions:
Loans charged off	0	30
Less recoveries on loans	0	0
Net loan charge-offs (recoveries)	0	30
Balance at end of period	638	895
Commercial real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	4,914	4,437
Additions:
Provision for loan losses	617	(421)
Deductions:
Loans charged off	8	14
Less recoveries on loans	0	(6)
Net loan charge-offs (recoveries)	8	8
Balance at end of period	5,523	4,008
Installment and other consumer
Summary of the allowance for loan losses
Balance at beginning of period	334	345
Additions:
Provision for loan losses	18	40
Deductions:
Loans charged off	52	57
Less recoveries on loans	(33)	(24)
Net loan charge-offs (recoveries)	19	33
Balance at end of period	333	352
Unallocated
Summary of the allowance for loan losses
Balance at beginning of period	199	79
Additions:
Provision for loan losses	(44)	55
Deductions:
Loans charged off	0	0
Less recoveries on loans	0	0
Net loan charge-offs (recoveries)	0	0
Balance at end of period	$ 155	$ 134