Loans - Aging Categories of Loans by Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Aging categories of loans by segment
Current	$ 1,325,684	$ 1,334,612
Past due 30 to 89 days	11,057	7,324
Past due 90 days or more & still accruing	1,503	2,047
Non-accrual	9,797	10,374
Total	1,348,041	1,354,357
Net deferred loan fees and discounts	1,359	1,187
Allowance for loan losses	(12,500)	(11,894)	$ (13,792)	$ (13,837)
Current loans, net	1,314,543	1,323,905
Loans, net	1,336,900	1,343,650
Commercial, financial, and agricultural
Aging categories of loans by segment
Current	155,692	153,737
Past due 30 to 89 days	489	249
Past due 90 days or more & still accruing	31	30
Non-accrual	1,938	2,197
Total	158,150	156,213
Allowance for loan losses	(1,897)	(1,779)	(1,732)	(1,680)
Real Estate Mortgages | Residential
Aging categories of loans by segment
Current	607,445	615,580
Past due 30 to 89 days	6,321	4,881
Past due 90 days or more & still accruing	1,383	1,529
Non-accrual	1,005	1,266
Total	616,154	623,256
Allowance for loan losses	(4,537)	(4,306)	(5,730)	(5,616)
Real Estate Mortgages | Commercial
Aging categories of loans by segment
Current	351,202	355,597
Past due 30 to 89 days	2,795	775
Past due 90 days or more & still accruing	0	164
Non-accrual	6,740	6,725
Total	360,737	363,261
Allowance for loan losses	(3,414)	(3,210)	(3,802)	(4,047)
Real Estate Mortgages | Construction
Aging categories of loans by segment
Current	39,003	37,871
Past due 30 to 89 days	230	131
Past due 90 days or more & still accruing	0	0
Non-accrual	64	65
Total	39,297	38,067
Allowance for loan losses	(160)	(118)	(130)	(143)
Consumer automobile loans
Aging categories of loans by segment
Current	150,891	149,703
Past due 30 to 89 days	700	709
Past due 90 days or more & still accruing	74	0
Non-accrual	50	105
Total	151,715	150,517
Allowance for loan losses	(1,855)	(1,780)	(1,402)	(1,328)
Other consumer installment loans
Aging categories of loans by segment
Current	21,451	22,124
Past due 30 to 89 days	522	579
Past due 90 days or more & still accruing	15	324
Non-accrual	0	16
Total	21,988	23,043
Allowance for loan losses	$ (267)	$ (278)	$ (278)	$ (259)