Loans (Residential, Home Equity and Consumer Loans Based on Payment Activity) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 3,120,981	$ 3,091,998		$ 3,081,973
Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	8,563	33,857
Fiscal Year Before Current Fiscal Year	28,248	16,486
Two Years Before Current Fiscal Year	9,381	8,467
Three Years Before Current Fiscal Year	7,577	2,117
Four Years Before Current Fiscal Year	1,671	924
Prior	2,790	2,268
Revolving Loans Amortized Cost Basis	2,340	2,598
Total	60,570	66,717	$ 69,264	81,217
Consumer Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	8,563	33,857
Fiscal Year Before Current Fiscal Year	28,248	16,486
Two Years Before Current Fiscal Year	9,349	8,456
Three Years Before Current Fiscal Year	7,567	2,115
Four Years Before Current Fiscal Year	1,669	910
Prior	2,757	2,245
Revolving Loans Amortized Cost Basis	2,305	2,563
Total	60,458	66,632
Consumer Loans | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year Before Current Fiscal Year	0	0
Two Years Before Current Fiscal Year	32	11
Three Years Before Current Fiscal Year	10	2
Four Years Before Current Fiscal Year	2	14
Prior	33	23
Revolving Loans Amortized Cost Basis	35	35
Total	112	85
Home Equity Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year Before Current Fiscal Year	0	0
Two Years Before Current Fiscal Year	0	34
Three Years Before Current Fiscal Year	55	46
Four Years Before Current Fiscal Year	46	67
Prior	540	490
Revolving Loans Amortized Cost Basis	211,665	218,711
Total	212,306	219,348	225,790	225,755
Home Equity Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year Before Current Fiscal Year	0	0
Two Years Before Current Fiscal Year	0	34
Three Years Before Current Fiscal Year	55	46
Four Years Before Current Fiscal Year	46	67
Prior	540	490
Revolving Loans Amortized Cost Basis	211,372	218,440
Total	212,013	219,077
Home Equity Loans | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year Before Current Fiscal Year	0	0
Two Years Before Current Fiscal Year	0	0
Three Years Before Current Fiscal Year	0	0
Four Years Before Current Fiscal Year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	293	271
Total	293	271
Residential Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	33,640	45,945
Fiscal Year Before Current Fiscal Year	45,639	26,536
Two Years Before Current Fiscal Year	22,574	28,050
Three Years Before Current Fiscal Year	23,597	28,764
Four Years Before Current Fiscal Year	27,040	25,155
Prior	115,144	101,826
Revolving Loans Amortized Cost Basis	0	0
Total	267,634	256,276	$ 305,002	$ 304,855
Residential Mortgage Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	33,640	45,945
Fiscal Year Before Current Fiscal Year	45,639	26,536
Two Years Before Current Fiscal Year	22,574	28,050
Three Years Before Current Fiscal Year	23,597	28,764
Four Years Before Current Fiscal Year	27,040	25,155
Prior	113,996	100,998
Revolving Loans Amortized Cost Basis	0	0
Total	266,486	255,448
Residential Mortgage Loans | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Current Fiscal Year	0	0
Fiscal Year Before Current Fiscal Year	0	0
Two Years Before Current Fiscal Year	0	0
Three Years Before Current Fiscal Year	0	0
Four Years Before Current Fiscal Year	0	0
Prior	1,148	828
Revolving Loans Amortized Cost Basis	0	0
Total	$ 1,148	$ 828