Loans and Allowance - Composition of Impaired Loans by Loan Class (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Unpaid Principal Balance
Impaired loans with no related allowance	$ 10,350		$ 9,955
Impaired loans with related allowance	5,254		5,139
Total Impaired Loans	15,604		15,094
Recorded Investment
Impaired loans with no related allowance	8,340		7,352
Impaired loans with related allowance	4,473		4,357
Total Impaired Loans	12,813		11,709
Related Allowance	616		689
Average Recorded Investment
Impaired loans with no related allowance	8,834	$ 20,149
Impaired loans with related allowance	4,973	4,576
Total Impaired Loans	13,807	24,725
Interest Income Recognized
Impaired loans with no related allowance	38	40
Impaired loans with related allowance	22	18
Total Impaired Loans	60	58
Commercial and industrial loans
Unpaid Principal Balance
Impaired loans with no related allowance	905		320
Recorded Investment
Impaired loans with no related allowance	905		320
Average Recorded Investment
Impaired loans with no related allowance	905	1,641
Interest Income Recognized
Impaired loans with no related allowance	0	0
Agricultural production financing and other loans to farmers
Unpaid Principal Balance
Impaired loans with no related allowance			299
Recorded Investment
Impaired loans with no related allowance			137
Average Recorded Investment
Impaired loans with no related allowance		799
Impaired loans with related allowance		2,150
Interest Income Recognized
Impaired loans with no related allowance		0
Construction
Unpaid Principal Balance
Impaired loans with no related allowance	1,206		1,206
Recorded Investment
Impaired loans with no related allowance	970		970
Average Recorded Investment
Impaired loans with no related allowance	1,015	8,270
Interest Income Recognized
Impaired loans with no related allowance	0	0
Commercial and farmland
Unpaid Principal Balance
Impaired loans with no related allowance	8,160		8,037
Impaired loans with related allowance	2,649		2,648
Recorded Investment
Impaired loans with no related allowance	6,403		5,849
Impaired loans with related allowance	1,909		1,909
Related Allowance	150		231
Average Recorded Investment
Impaired loans with no related allowance	6,852	8,999
Impaired loans with related allowance	2,400	171
Interest Income Recognized
Impaired loans with no related allowance	37	39
Residential
Unpaid Principal Balance
Impaired loans with no related allowance	76		93
Impaired loans with related allowance	2,198		2,070
Recorded Investment
Impaired loans with no related allowance	59		76
Impaired loans with related allowance	2,173		2,044
Related Allowance	393		383
Average Recorded Investment
Impaired loans with no related allowance	59	38
Impaired loans with related allowance	2,180	1,884
Interest Income Recognized
Impaired loans with no related allowance	1	1
Impaired loans with related allowance	19	15
Home equity
Unpaid Principal Balance
Impaired loans with related allowance	407		417
Recorded Investment
Impaired loans with related allowance	391		400
Related Allowance	73		75
Average Recorded Investment
Impaired loans with no related allowance		48
Impaired loans with related allowance	393	356
Interest Income Recognized
Impaired loans with related allowance	3	3
Individuals' loans for household and other personal expenditures
Unpaid Principal Balance
Impaired loans with no related allowance	3
Impaired loans with related allowance			4
Recorded Investment
Impaired loans with no related allowance	3
Impaired loans with related allowance			4
Related Allowance			$ 0
Average Recorded Investment
Impaired loans with no related allowance	$ 3	1
Interest Income Recognized
Impaired loans with no related allowance		0
Public finance and other commercial loans
Average Recorded Investment
Impaired loans with no related allowance		353
Impaired loans with related allowance		15
Interest Income Recognized
Impaired loans with no related allowance		0
Impaired loans with related allowance		$ 0