Loans and Allowance for Credit Losses - Composition of Impaired Loans by Loan Class (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Unpaid Principal Balance
Impaired loans with no related allowance	$ 9,101	$ 9,955
Impaired loans with related allowance	49,513	5,139
Total Impaired Loans	58,614	15,094
Recorded Investment
Impaired loans with no related allowance	7,813	7,352
Impaired loans with related allowance	48,343	4,357
Total Impaired Loans	56,156	11,709
Related Allowance	12,901	689
Average Recorded Investment
Impaired loans with no related allowance	8,113	7,924
Impaired loans with related allowance	49,003	4,405
Total Impaired Loans	57,116	12,329
Interest Income Recognized
Impaired loans with no related allowance	148	159
Impaired loans with related allowance	84	75
Total Impaired Loans	232	234
Commercial and industrial loans
Unpaid Principal Balance
Impaired loans with no related allowance	1,059	320
Impaired loans with related allowance	268
Recorded Investment
Impaired loans with no related allowance	991	320
Impaired loans with related allowance	268
Related Allowance	223
Average Recorded Investment
Impaired loans with no related allowance	991	320
Impaired loans with related allowance	267
Interest Income Recognized
Impaired loans with no related allowance	0	0
Impaired loans with related allowance	0
Agricultural land, production and other loans to farmers
Unpaid Principal Balance
Impaired loans with no related allowance		752
Impaired loans with related allowance	640	588
Recorded Investment
Impaired loans with no related allowance		381
Impaired loans with related allowance	562	585
Related Allowance	3	107
Average Recorded Investment
Impaired loans with no related allowance		542
Impaired loans with related allowance	589	585
Interest Income Recognized
Impaired loans with no related allowance		0
Impaired loans with related allowance	0	0
Construction
Unpaid Principal Balance
Impaired loans with no related allowance		1,206
Recorded Investment
Impaired loans with no related allowance		970
Average Recorded Investment
Impaired loans with no related allowance		1,229
Interest Income Recognized
Impaired loans with no related allowance		0
Commercial real estate, non-owner occupied
Unpaid Principal Balance
Impaired loans with no related allowance	4,958	6,202
Impaired loans with related allowance	44,016
Recorded Investment
Impaired loans with no related allowance	4,694	5,299
Impaired loans with related allowance	43,715
Related Allowance	11,686
Average Recorded Investment
Impaired loans with no related allowance	4,850	5,399
Impaired loans with related allowance	44,119
Interest Income Recognized
Impaired loans with no related allowance	145	156
Impaired loans with related allowance	0
Commercial real estate, owner occupied
Unpaid Principal Balance
Impaired loans with no related allowance	2,125	1,382
Impaired loans with related allowance	2,061	2,060
Recorded Investment
Impaired loans with no related allowance	1,310	306
Impaired loans with related allowance	1,323	1,324
Related Allowance	557	124
Average Recorded Investment
Impaired loans with no related allowance	1,429	357
Impaired loans with related allowance	1,447	1,324
Interest Income Recognized
Impaired loans with no related allowance	0	0
Impaired loans with related allowance	0	0
Residential
Unpaid Principal Balance
Impaired loans with no related allowance	957	93
Impaired loans with related allowance	2,041	2,070
Recorded Investment
Impaired loans with no related allowance	816	76
Impaired loans with related allowance	2,014	2,044
Related Allowance	352	383
Average Recorded Investment
Impaired loans with no related allowance	840	77
Impaired loans with related allowance	2,108	2,083
Interest Income Recognized
Impaired loans with no related allowance	3	3
Impaired loans with related allowance	70	63
Home equity
Unpaid Principal Balance
Impaired loans with related allowance	487	417
Recorded Investment
Impaired loans with related allowance	461	400
Related Allowance	80	75
Average Recorded Investment
Impaired loans with related allowance	473	409
Interest Income Recognized
Impaired loans with related allowance	14	12
Individuals' loans for household and other personal expenditures
Unpaid Principal Balance
Impaired loans with no related allowance	2
Impaired loans with related allowance		4
Recorded Investment
Impaired loans with no related allowance	2
Impaired loans with related allowance		4
Related Allowance		0
Average Recorded Investment
Impaired loans with no related allowance	3
Impaired loans with related allowance		4
Interest Income Recognized
Impaired loans with no related allowance	$ 0
Impaired loans with related allowance		$ 0