Loans - Allowance for Credit Losses on Financing Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Allowance for Loan Losses:
Beginning Balance	$ 12,500	$ 13,792	$ 11,894	$ 13,837
Charge-offs	(231)	(209)	(461)	(667)
Recoveries	63	103	149	156
Provision for loan losses	645	315	1,395	675
Ending Balance	12,977	14,001	12,977	14,001
Commercial, financial, and agricultural
Allowance for Loan Losses:
Beginning Balance	1,897	1,732	1,779	1,680
Charge-offs	(8)	(30)	(22)	(80)
Recoveries	2	36	23	42
Provision for loan losses	62	(154)	173	(58)
Ending Balance	1,953	1,584	1,953	1,584
Real Estate Mortgages | Residential
Allowance for Loan Losses:
Beginning Balance	4,537	5,730	4,306	5,616
Charge-offs	(127)	(64)	(168)	(137)
Recoveries	26	0	47	1
Provision for loan losses	42	83	293	269
Ending Balance	4,478	5,749	4,478	5,749
Real Estate Mortgages | Commercial
Allowance for Loan Losses:
Beginning Balance	3,414	3,802	3,210	4,047
Charge-offs	0	(11)	0	(150)
Recoveries	0	1	0	1
Provision for loan losses	(79)	(269)	125	(375)
Ending Balance	3,335	3,523	3,335	3,523
Real Estate Mortgages | Construction
Allowance for Loan Losses:
Beginning Balance	160	130	118	143
Charge-offs	0	0	0	0
Recoveries	3	2	5	7
Provision for loan losses	(13)	0	27	(18)
Ending Balance	150	132	150	132
Consumer automobile loans
Allowance for Loan Losses:
Beginning Balance	1,855	1,402	1,780	1,328
Charge-offs	(14)	(38)	(89)	(138)
Recoveries	6	34	7	60
Provision for loan losses	367	37	516	185
Ending Balance	2,214	1,435	2,214	1,435
Other consumer installment loans
Allowance for Loan Losses:
Beginning Balance	267	278	278	259
Charge-offs	(82)	(66)	(182)	(162)
Recoveries	26	30	67	45
Provision for loan losses	(84)	(2)	(36)	98
Ending Balance	127	240	127	240
Unallocated
Allowance for Loan Losses:
Beginning Balance	370	718	423	764
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	350	620	297	574
Ending Balance	$ 720	$ 1,338	$ 720	$ 1,338