Past Due Loans, Allowance For Credit Losses, Non-Accrual Loans, and TDRS - TDRs By Class (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	$ 539	$ 813
Non-accrual	6,726	11,703
Total	7,265	12,516	$ 16,678
Eligible modifications, outstanding balance	40,600
Specific reserves related to TDRs	245	140
Commercial, industrial, agricultural | Commercial and industrial
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	6,255	8,859
Total	6,255	8,859
Commercial, industrial, agricultural | Agricultural
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	0	0
Total	0	0
Commercial real estate
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	155	184
Non-accrual	151	2,500
Total	306	2,684
Commercial real estate | Office, retail, and industrial
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	0	2,340
Total	0	2,340
Commercial real estate | Multi- family
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	151	160
Total	151	160
Commercial real estate | Construction
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	0	0
Total	0	0
Commercial real estate | Other commercial real estate
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	155	184
Non-accrual	0	0
Total	155	184
Total corporate loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	155	184
Non-accrual	6,406	11,359
Total	6,561	11,543
Consumer
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	384	629
Non-accrual	320	344
Total	704	973
Consumer | Home equity
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	29	31
Non-accrual	103	116
Total	132	147
Consumer | 1-4 family mortgages
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	355	598
Non-accrual	217	228
Total	572	826
Consumer | Installment
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	0	0
Total	$ 0	$ 0