Loans (Collateral-dependent Loans by Class) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 3,120,981	$ 3,091,998		$ 3,081,973
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	20,689	21,121
Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,846	3,018
Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	639	669
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,505	1,687
Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	25,679	26,495
Commercial and Industrial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	672,300	638,773	$ 534,692	589,758
Commercial and Industrial Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	4,350	4,943
Commercial and Industrial Loans | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,846	3,014
Commercial and Industrial Loans | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	639	669
Commercial and Industrial Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	30	154
Commercial and Industrial Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	7,865	8,780
Commercial Real Estate Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,492,617	1,467,397	1,500,247	1,495,862
Commercial Real Estate Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	11,629	11,877
Commercial Real Estate Loans | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Commercial Real Estate Loans | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Commercial Real Estate Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,472	1,530
Commercial Real Estate Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	13,101	13,407
Agricultural Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	347,231	376,186	384,654	384,526
Agricultural Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,980	3,064
Agricultural Loans | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Agricultural Loans | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Agricultural Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Agricultural Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,980	3,064
Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	55,714	55,664	57,257
Leases | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Leases | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Leases | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Leases | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Leases | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Home Equity Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	212,306	219,348	225,790	225,755
Home Equity Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	406	416
Home Equity Loans | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Home Equity Loans | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Home Equity Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Home Equity Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	406	416
Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	60,570	66,717	69,264	81,217
Consumer Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	4	4
Consumer Loans | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	4
Consumer Loans | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Consumer Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	3	3
Consumer Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	7	11
Credit Cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	12,609	11,637	11,953
Credit Cards | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Credit Cards | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Credit Cards | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Credit Cards | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Credit Cards | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Residential Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	267,634	256,276	$ 305,002	$ 304,855
Residential Mortgage Loans | Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,320	817
Residential Mortgage Loans | Equipment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Residential Mortgage Loans | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Residential Mortgage Loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Residential Mortgage Loans | Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 1,320	$ 817