Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies [Line Items]
Concentration of credit, benchmark description	Otherwise, there were no concentrations of credit to any industry equaling more than 15% of total capital.
Maturity of interest-bearing time deposits	5 years
Held-to-maturity securities	$ 0	$ 0
Net unamortized origination costs	$ 298,000	70,000
Usual period of lines of credit for commercial, financial and agricultural lending	5 years
Goodwill impairment loss	$ 0	0
Mortgage servicing rights	158,000	180,000
Investment in low-income housing limited partnership	3,105,000	3,904,000
Accrued benefit liability	1,146,000	1,117,000
Other postretirement benefit	29,000	36,000
Advertising expense	270,000	312,000
Shareholder Service [Member]
Summary of Significant Accounting Policies [Line Items]
Trust and Estate fees recognized	$ 76,000	$ 88,000
Leasehold Improvements [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment, description	shorter of the assets’ useful life or the related lease term
Residential Portfolio Segment [Member] | Credit Exposure [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of capital representing credit exposure to lessors	39.00%
Residential Portfolio Segment [Member] | Home Equity Lines of Credit [Member]
Summary of Significant Accounting Policies [Line Items]
Loan period for lending, maximum	20 years
Maximum loan-to-value ratio	90.00%
Residential Portfolio Segment [Member] | Home Equity Installments [Member]
Summary of Significant Accounting Policies [Line Items]
Loan period for lending, maximum	15 years
Maximum loan-to-value ratio	80.00%
Real Estate Portfolio Segment [Member] | Credit Exposure [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of capital representing credit exposure to lessors	27.00%
Real Estate Portfolio Segment [Member] | Commercial Loan [Member]
Summary of Significant Accounting Policies [Line Items]
Loan period for lending, maximum	20 years
Maximum loan-to-value ratio	80.00%
Commercial Portfolio Segment [Member] | Credit Exposure [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of capital representing credit exposure to lessors	31.00%
Consumer Portfolio Segment [Member] | Mortgage Loan [Member]
Summary of Significant Accounting Policies [Line Items]
Loan period for lending, maximum	25 years
Maximum loan-to-value ratio	80.00%
Non-Residential Portfolio [Member] | Credit Exposure [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of capital representing credit exposure to lessors	44.00%
Maximum [Member] | Furniture and Equipment [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment	10 years
Maximum [Member] | Building [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment	40 years
Minimum [Member] | Furniture and Equipment [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment	3 years
Minimum [Member] | Building [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment	25 years