Loans (Aging of Past Due Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 17,736	$ 20,489
Loans Not Past Due	3,103,245	3,071,509
Total	3,120,981	3,091,998		$ 3,081,973
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4,582	5,219
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	536	7,545
Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	12,618	7,725
Commercial and Industrial Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	3,095	3,827
Loans Not Past Due	669,205	634,946
Total	672,300	638,773	$ 534,692	589,758
Commercial and Industrial Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	729	477
Commercial and Industrial Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	384	909
Commercial and Industrial Loans | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,982	2,441
Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	8,684	8,564
Loans Not Past Due	1,483,933	1,458,833
Total	1,492,617	1,467,397	1,500,247	1,495,862
Commercial Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	158	5
Commercial Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	4,877
Commercial Real Estate Loans | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,526	3,682
Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	651	651
Loans Not Past Due	346,580	375,535
Total	347,231	376,186	384,654	384,526
Agricultural Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Agricultural Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Agricultural Loans | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	651	651
Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Loans Not Past Due	55,714	55,664
Total	55,714	55,664	57,257
Leases | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Leases | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Leases | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	694	948
Loans Not Past Due	211,612	218,400
Total	212,306	219,348	225,790	225,755
Home Equity Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	327	672
Home Equity Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	74	5
Home Equity Loans | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	293	271
Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	460	382
Loans Not Past Due	60,110	66,335
Total	60,570	66,717	69,264	81,217
Consumer Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	328	233
Consumer Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	38	84
Consumer Loans | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	94	65
Credit Cards
Financing Receivable, Past Due [Line Items]
Total Past Due	185	261
Loans Not Past Due	12,424	11,376
Total	12,609	11,637	11,953
Credit Cards | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	26	95
Credit Cards | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5	80
Credit Cards | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	154	86
Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	3,967	5,856
Loans Not Past Due	263,667	250,420
Total	267,634	256,276	$ 305,002	$ 304,855
Residential Mortgage Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,014	3,737
Residential Mortgage Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	35	1,590
Residential Mortgage Loans | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 918	$ 529