Loans and Allowance for Loan Losses - Impairment Methodology (Details) - USD ($)	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Allowance for loan losses:
Individually evaluated for impairment	$ 710,000		$ 615,000
Collectively evaluated for impairment	15,912,000		11,862,000
Total	16,622,000	$ 15,693,000	12,477,000	$ 11,883,000	$ 11,845,000	$ 11,652,000
Loans outstanding:
Individually evaluated for impairment	11,338,000		7,395,000
Collectively evaluated for impairment	1,269,277,000		1,161,402,000
Total	1,280,615,000		1,168,797,000
Commercial, financial, and agricultural
Allowance for loan losses:
Individually evaluated for impairment	291,000		311,000
Collectively evaluated for impairment	3,323,000		2,607,000
Total	3,614,000	3,623,000	2,918,000	2,783,000	3,232,000	3,237,000
Loans outstanding:
Individually evaluated for impairment	3,538,000		1,514,000
Collectively evaluated for impairment	292,785,000		197,508,000
Total	296,323,000		199,022,000
Residential real estate | Construction
Allowance for loan losses:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	171,000		64,000
Total	171,000	117,000	64,000	69,000	74,000	140,000
Loans outstanding:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	27,188,000		23,035,000
Total	27,188,000		23,035,000
Residential real estate | Mortgages
Allowance for loan losses:
Individually evaluated for impairment	231,000		264,000
Collectively evaluated for impairment	2,480,000		1,854,000
Total	2,711,000	2,363,000	2,118,000	1,772,000	1,890,000	2,071,000
Loans outstanding:
Individually evaluated for impairment	4,857,000		3,856,000
Collectively evaluated for impairment	245,595,000		248,787,000
Total	250,452,000		252,643,000
Commercial real estate | Construction
Allowance for loan losses:
Individually evaluated for impairment	122,000		0
Collectively evaluated for impairment	600,000		369,000
Total	722,000	622,000	369,000	704,000	638,000	757,000
Loans outstanding:
Individually evaluated for impairment	959,000		137,000
Collectively evaluated for impairment	84,050,000		84,861,000
Total	85,009,000		84,998,000
Commercial real estate | Mortgages
Allowance for loan losses:
Individually evaluated for impairment	52,000		23,000
Collectively evaluated for impairment	8,996,000		6,524,000
Total	9,048,000	8,614,000	6,547,000	6,109,000	5,523,000	4,914,000
Loans outstanding:
Individually evaluated for impairment	1,866,000		1,711,000
Collectively evaluated for impairment	590,989,000		574,924,000
Total	592,855,000		576,635,000
Installment and other consumer
Allowance for loan losses:
Individually evaluated for impairment	14,000		17,000
Collectively evaluated for impairment	292,000		364,000
Total	306,000	351,000	381,000	307,000	333,000	334,000
Loans outstanding:
Individually evaluated for impairment	118,000		177,000
Collectively evaluated for impairment	28,670,000		32,287,000
Total	28,788,000		32,464,000
Unallocated
Allowance for loan losses:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	50,000		80,000
Total	50,000	$ 3,000	80,000	$ 139,000	$ 155,000	$ 199,000
Loans outstanding:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	0		0
Total	$ 0		$ 0