Loans - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Credit quality categories
Total	$ 1,383,524	$ 1,383,893
Pass
Credit quality categories
Total	1,353,623	1,352,601
Special Mention
Credit quality categories
Total	10,570	10,707
Substandard
Credit quality categories
Total	19,331	20,585
Commercial, financial, and agricultural
Credit quality categories
Total	194,917	188,561
Commercial, financial, and agricultural | Pass
Credit quality categories
Total	186,169	179,840
Commercial, financial, and agricultural | Special Mention
Credit quality categories
Total	3,430	3,426
Commercial, financial, and agricultural | Substandard
Credit quality categories
Total	5,318	5,295
Consumer automobile loans
Credit quality categories
Total	139,837	133,183
Consumer automobile loans | Pass
Credit quality categories
Total	139,837	133,183
Consumer automobile loans | Special Mention
Credit quality categories
Total	0	0
Consumer automobile loans | Substandard
Credit quality categories
Total	0	0
Other consumer installment loans
Credit quality categories
Total	23,841	24,552
Other consumer installment loans | Pass
Credit quality categories
Total	23,841	24,552
Other consumer installment loans | Special Mention
Credit quality categories
Total	0	0
Other consumer installment loans | Substandard
Credit quality categories
Total	0	0
Residential | Real Estate Mortgages
Credit quality categories
Total	618,559	622,379
Residential | Real Estate Mortgages | Pass
Credit quality categories
Total	616,004	619,800
Residential | Real Estate Mortgages | Special Mention
Credit quality categories
Total	691	694
Residential | Real Estate Mortgages | Substandard
Credit quality categories
Total	1,864	1,885
Commercial | Real Estate Mortgages
Credit quality categories
Total	367,089	371,695
Commercial | Real Estate Mortgages | Pass
Credit quality categories
Total	348,504	351,703
Commercial | Real Estate Mortgages | Special Mention
Credit quality categories
Total	6,449	6,587
Commercial | Real Estate Mortgages | Substandard
Credit quality categories
Total	12,136	13,405
Construction | Real Estate Mortgages
Credit quality categories
Total	39,281	43,523
Construction | Real Estate Mortgages | Pass
Credit quality categories
Total	39,268	43,523
Construction | Real Estate Mortgages | Special Mention
Credit quality categories
Total	0	0
Construction | Real Estate Mortgages | Substandard
Credit quality categories
Total	$ 13