Past Due Loans, Allowance For Credit Losses, Non-Accrual Loans, and TDRS - TDRs By Class (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		$ 1,201	$ 1,233
Non-accrual	[1]	12,093	20,514
Total		13,294	21,747	$ 9,282
Specific reserves related to TDRs		2,400	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 TDRs		188	227
Non-accrual	[1]	9,336	16,420
Total		9,524	16,647
Commercial Industrial And Agricultural | Agricultural
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		0	0
Non-accrual	[1]	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 TDRs		358	333
Non-accrual	[1]	2,340	3,600
Total		2,698	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 TDRs		0	0
Non-accrual	[1]	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 TDRs		160	163
Non-accrual	[1]	0	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 TDRs		0	0
Non-accrual	[1]	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 TDRs		198	170
Non-accrual	[1]	0	0
Total		198	170
Total corporate loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		546	560
Non-accrual	[1]	11,676	20,020
Total		12,222	20,580
Consumer loans
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		655	673
Non-accrual	[1]	417	494
Total		1,072	1,167
Consumer loans | Home equity
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		31	36
Non-accrual	[1]	179	240
Total		210	276
Consumer loans | 1-4 family mortgages
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		624	637
Non-accrual	[1]	238	0
Total		862	637
Consumer loans | Installment
Past Due Loans, Allowance For Credit Losses, and Impaired Loans (Details) - TDRs By Class [Line Items]
Accruing TDRs		0	0
Non-accrual	[1]	0	254
Total		$ 0	$ 254

[1] These TDRs are included in non-accrual loans in the preceding tables.