Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Summary of the allowance for loan losses
Balance at beginning of period	$ 11,883	$ 11,212	$ 11,652	$ 10,852
Additions:
Provision for loan losses	450	250	850	1,000
Deductions:
Loans charged off	213	186	693	735
Less recoveries on loans	(58)	(82)	(369)	(241)
Net loan charge-offs (recoveries)	155	104	324	494
Balance at end of period	12,178	11,358	12,178	11,358
Commercial, financial, and agricultural
Summary of the allowance for loan losses
Balance at beginning of period	2,783	3,943	3,237	3,325
Additions:
Provision for loan losses	155	(420)	(232)	478
Deductions:
Loans charged off	61	75	255	378
Less recoveries on loans	(12)	(38)	(139)	(61)
Net loan charge-offs (recoveries)	49	37	116	317
Balance at end of period	2,889	3,486	2,889	3,486
Residential real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	69	201	140	170
Additions:
Provision for loan losses	3	26	(81)	80
Deductions:
Loans charged off	0	0		48
Less recoveries on loans	(12)	(13)	(25)	(38)
Net loan charge-offs (recoveries)	(12)	(13)	(25)	10
Balance at end of period	84	240	84	240
Residential real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	1,772	2,109	2,071	1,689
Additions:
Provision for loan losses	252	255	30	672
Deductions:
Loans charged off	86	32	266	64
Less recoveries on loans	(8)	(9)	(111)	(44)
Net loan charge-offs (recoveries)	78	23	155	20
Balance at end of period	1,946	2,341	1,946	2,341
Commercial real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	704	905	757	807
Additions:
Provision for loan losses	97	(159)	44	(31)
Deductions:
Loans charged off	0	0		30
Less recoveries on loans	0	0
Net loan charge-offs (recoveries)	0	0		30
Balance at end of period	801	746	801	746
Commercial real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	6,109	3,630	4,914	4,437
Additions:
Provision for loan losses	(15)	444	1,193	(366)
Deductions:
Loans charged off	6	5	21	34
Less recoveries on loans	(7)	(2)	(9)	(34)
Net loan charge-offs (recoveries)	(1)	3	12
Balance at end of period	6,095	4,071	6,095	4,071
Installment and other consumer
Summary of the allowance for loan losses
Balance at beginning of period	307	413	334	345
Additions:
Provision for loan losses	62	39	60	170
Deductions:
Loans charged off	60	74	151	181
Less recoveries on loans	(19)	(20)	(85)	(64)
Net loan charge-offs (recoveries)	41	54	66	117
Balance at end of period	328	398	328	398
Unallocated
Summary of the allowance for loan losses
Balance at beginning of period	139	11	199	79
Additions:
Provision for loan losses	(104)	65	(164)	(3)
Deductions:
Loans charged off	0	0
Less recoveries on loans	0	0
Net loan charge-offs (recoveries)	0	0
Balance at end of period	$ 35	$ 76	$ 35	$ 76