Loans - Allowance for Credit Losses on Financing Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for Loan Losses:
Beginning Balance	$ 12,977	$ 14,001	$ 11,894	$ 13,837
Charge-offs	(239)	(221)	(700)	(888)
Recoveries	46	109	195	265
Provision for loan losses	645	360	2,040	1,035
Ending Balance	13,429	14,249	13,429	14,249
Commercial, financial, and agricultural
Allowance for Loan Losses:
Beginning Balance	1,953	1,584	1,779	1,680
Charge-offs	0	0	(22)	(80)
Recoveries	9	43	32	84
Provision for loan losses	17	159	190	102
Ending Balance	1,979	1,786	1,979	1,786
Real Estate Mortgages | Residential
Allowance for Loan Losses:
Beginning Balance	4,478	5,749	4,306	5,616
Charge-offs	(6)	(114)	(174)	(251)
Recoveries	1	2	48	3
Provision for loan losses	(24)	4	269	273
Ending Balance	4,449	5,641	4,449	5,641
Real Estate Mortgages | Commercial
Allowance for Loan Losses:
Beginning Balance	3,335	3,523	3,210	4,047
Charge-offs	0	0	0	(150)
Recoveries	0	0	0	1
Provision for loan losses	(290)	(12)	(165)	(387)
Ending Balance	3,045	3,511	3,045	3,511
Real Estate Mortgages | Construction
Allowance for Loan Losses:
Beginning Balance	150	132	118	143
Charge-offs	0	0	0	0
Recoveries	0	2	5	10
Provision for loan losses	20	22	47	3
Ending Balance	170	156	170	156
Consumer automobile loans
Allowance for Loan Losses:
Beginning Balance	2,214	1,435	1,780	1,328
Charge-offs	(200)	(34)	(289)	(172)
Recoveries	10	14	17	74
Provision for loan losses	(27)	(41)	489	144
Ending Balance	1,997	1,374	1,997	1,374
Other consumer installment loans
Allowance for Loan Losses:
Beginning Balance	127	240	278	259
Charge-offs	(33)	(73)	(215)	(235)
Recoveries	26	48	93	93
Provision for loan losses	135	27	99	125
Ending Balance	255	242	255	242
Unallocated
Allowance for Loan Losses:
Beginning Balance	720	1,338	423	764
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan losses	814	201	1,111	775
Ending Balance	$ 1,534	$ 1,539	$ 1,534	$ 1,539