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, 2020	Dec. 31, 2019	Sep. 30, 2019
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	$ 841	$ 1,233
Non-accrual	15,837	20,514
Total	16,678	21,747	$ 6,510
Specific reserves related to TDRs	186	2,200
Commercial industrial and agricultural | Commercial and industrial
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	227
Non-accrual	12,982	16,420
Total	12,982	16,647
Commercial industrial and 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	193	333
Non-accrual	2,500	3,600
Total	2,693	3,933
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	2,340	3,600
Total	2,340	3,600
Commercial real estate | Multi-family
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	163
Non-accrual	160	0
Total	160	163
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	193	170
Non-accrual	0	0
Total	193	170
Total corporate loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	193	560
Non-accrual	15,482	20,020
Total	15,675	20,580
Consumer loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	648	673
Non-accrual	355	494
Total	1,003	1,167
Consumer loans | Home equity
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	31	36
Non-accrual	123	240
Total	154	276
Consumer loans | 1-4 family mortgages
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	617	637
Non-accrual	232	0
Total	849	637
Consumer loans | Installment
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing	0	0
Non-accrual	0	254
Total	$ 0	$ 254