Loans - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Ending allowance balance attributable to loans:
Individually evaluated for impairment	$ 1,107		$ 1,393
Collectively evaluated for impairment	12,322		10,501
Total ending allowance balance	13,429	$ 12,977	11,894	$ 14,249	$ 14,001	$ 13,837
Loans:
Individually evaluated for impairment	14,677		17,247
Collectively evaluated for impairment	1,333,387		1,337,110
Total	1,348,064		1,354,357
Commercial, financial, and agricultural
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	1,979		1,779
Total ending allowance balance	1,979	1,953	1,779	1,786	1,584	1,680
Loans:
Individually evaluated for impairment	1,835		2,285
Collectively evaluated for impairment	171,319		153,928
Total	173,154		156,213
Real Estate Mortgages | Residential
Ending allowance balance attributable to loans:
Individually evaluated for impairment	187		211
Collectively evaluated for impairment	4,262		4,095
Total ending allowance balance	4,449	4,478	4,306	5,641	5,749	5,616
Loans:
Individually evaluated for impairment	5,577		6,176
Collectively evaluated for impairment	589,541		617,080
Total	595,118		623,256
Real Estate Mortgages | Commercial
Ending allowance balance attributable to loans:
Individually evaluated for impairment	920		1,104
Collectively evaluated for impairment	2,125		2,106
Total ending allowance balance	3,045	3,335	3,210	3,511	3,523	4,047
Loans:
Individually evaluated for impairment	7,205		8,575
Collectively evaluated for impairment	348,516		354,686
Total	355,721		363,261
Real Estate Mortgages | Construction
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	170		118
Total ending allowance balance	170	150	118	156	132	143
Loans:
Individually evaluated for impairment	60		65
Collectively evaluated for impairment	43,140		38,002
Total	43,200		38,067
Consumer automobile loans
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		62
Collectively evaluated for impairment	1,997		1,718
Total ending allowance balance	1,997	2,214	1,780	1,374	1,435	1,328
Loans:
Individually evaluated for impairment	0		130
Collectively evaluated for impairment	160,201		150,387
Total	160,201		150,517
Other consumer installment loans
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		16
Collectively evaluated for impairment	255		262
Total ending allowance balance	255	127	278	242	240	259
Loans:
Individually evaluated for impairment	0		16
Collectively evaluated for impairment	20,670		23,027
Total	20,670		23,043
Unallocated
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	1,534		423
Total ending allowance balance	$ 1,534	$ 720	$ 423	$ 1,539	$ 1,338	$ 764