Loans and Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Summary of the allowance for loan losses
Balance at beginning of period	$ 11,845	$ 10,947	$ 11,652	$ 10,852
Additions:
Provision for loan losses	250	450	400	750
Deductions:
Loans charged off	283	269	480	548
Less recoveries on loans	(71)	(84)	(311)	(158)
Net loan charge-offs (recoveries)	212	185	169	390
Balance at end of period	11,883	11,212	11,883	11,212
Commercial, financial, and agricultural
Summary of the allowance for loan losses
Balance at beginning of period	3,232	3,261	3,237	3,325
Additions:
Provision for loan losses	(327)	865	(388)	898
Deductions:
Loans charged off	140	193	193	303
Less recoveries on loans	(18)	(10)	(127)	(23)
Net loan charge-offs (recoveries)	122	183	66	280
Balance at end of period	2,783	3,943	2,783	3,943
Residential real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	74	240	140	170
Additions:
Provision for loan losses	(17)	(52)	(83)	54
Deductions:
Loans charged off	0	0		48
Less recoveries on loans	(12)	(13)	(12)	(25)
Net loan charge-offs (recoveries)	(12)	(13)	(12)	23
Balance at end of period	69	201	69	201
Residential real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	1,890	2,057	2,071	1,689
Additions:
Provision for loan losses	(27)	48	(223)	416
Deductions:
Loans charged off	96	12	180	32
Less recoveries on loans	(5)	(16)	(104)	(36)
Net loan charge-offs (recoveries)	91	(4)	76	(4)
Balance at end of period	1,772	2,109	1,772	2,109
Commercial real estate | Construction
Summary of the allowance for loan losses
Balance at beginning of period	638	895	757	807
Additions:
Provision for loan losses	66	10	(53)	128
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	704	905	704	905
Commercial real estate | Mortgages
Summary of the allowance for loan losses
Balance at beginning of period	5,523	4,008	4,914	4,437
Additions:
Provision for loan losses	591	(388)	1,208	(809)
Deductions:
Loans charged off	8	15	16	29
Less recoveries on loans	(3)	(25)	(3)	(31)
Net loan charge-offs (recoveries)	5	(10)	13	(2)
Balance at end of period	6,109	3,630	6,109	3,630
Installment and other consumer
Summary of the allowance for loan losses
Balance at beginning of period	333	352	334	345
Additions:
Provision for loan losses	(20)	90	(1)	131
Deductions:
Loans charged off	39	49	91	106
Less recoveries on loans	(33)	(20)	(65)	(43)
Net loan charge-offs (recoveries)	6	29	26	63
Balance at end of period	307	413	307	413
Unallocated
Summary of the allowance for loan losses
Balance at beginning of period	155	134	199	79
Additions:
Provision for loan losses	(16)	(123)	(60)	(68)
Deductions:
Loans charged off	0	0
Less recoveries on loans	0	0
Net loan charge-offs (recoveries)	0	0
Balance at end of period	$ 139	$ 11	$ 139	$ 11