Securities Held to Maturity (Summary of Amortized Cost, Unrealized Gains, Unrealized Losses and Estimated Fair Values) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 98,995	$ 99,914
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,406	3,271
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	13	28
Debt Securities, Held-to-maturity, Fair Value	102,388	103,157
Tax Exempt State and Political Subdivisions General Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	72,500	73,179
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	2,770	2,524
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	75,270	75,703
Tax Exempt State and Political Subdivisions Water and Sewer Revenues [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	8,284	8,375
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	208	256
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	8,492	8,631
Tax Exempt State and Political Subdivisions Lease Revenues [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,356	4,395
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	64	88
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	4,420	4,483
Tax Exempt State and Political Subdivisions Sales Tax Revenues [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,616	4,649
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	81	94
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	3	3
Debt Securities, Held-to-maturity, Fair Value	4,694	4,740
Tax Exempt State and Political Subdivisions Other Revenues [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	9,239	9,316
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	283	309
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	10	25
Debt Securities, Held-to-maturity, Fair Value	$ 9,512	$ 9,600