Loans - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Credit quality categories
Total	$ 1,348,064	$ 1,354,357
Pass
Credit quality categories
Total	1,324,405	1,328,050
Special Mention
Credit quality categories
Total	13,836	10,690
Substandard
Credit quality categories
Total	9,823	15,617
Commercial, financial, and agricultural
Credit quality categories
Total	173,154	156,213
Commercial, financial, and agricultural | Pass
Credit quality categories
Total	167,073	149,349
Commercial, financial, and agricultural | Special Mention
Credit quality categories
Total	4,516	3,174
Commercial, financial, and agricultural | Substandard
Credit quality categories
Total	1,565	3,690
Consumer automobile
Credit quality categories
Total	160,201	150,517
Consumer automobile | Pass
Credit quality categories
Total	160,184	150,517
Consumer automobile | Special Mention
Credit quality categories
Total	0	0
Consumer automobile | Substandard
Credit quality categories
Total	17	0
Other consumer installment loans
Credit quality categories
Total	20,670	23,043
Other consumer installment loans | Pass
Credit quality categories
Total	20,667	23,039
Other consumer installment loans | Special Mention
Credit quality categories
Total	0	0
Other consumer installment loans | Substandard
Credit quality categories
Total	3	4
Residential | Real Estate Mortgages
Credit quality categories
Total	595,118	623,256
Residential | Real Estate Mortgages | Pass
Credit quality categories
Total	592,131	618,350
Residential | Real Estate Mortgages | Special Mention
Credit quality categories
Total	1,320	2,436
Residential | Real Estate Mortgages | Substandard
Credit quality categories
Total	1,667	2,470
Commercial | Real Estate Mortgages
Credit quality categories
Total	355,721	363,261
Commercial | Real Estate Mortgages | Pass
Credit quality categories
Total	341,309	348,864
Commercial | Real Estate Mortgages | Special Mention
Credit quality categories
Total	7,960	5,080
Commercial | Real Estate Mortgages | Substandard
Credit quality categories
Total	6,452	9,317
Construction | Real Estate Mortgages
Credit quality categories
Total	43,200	38,067
Construction | Real Estate Mortgages | Pass
Credit quality categories
Total	43,041	37,931
Construction | Real Estate Mortgages | Special Mention
Credit quality categories
Total	40	0
Construction | Real Estate Mortgages | Substandard
Credit quality categories
Total	$ 119	$ 136