Securities Held to Maturity (Summary of Amortized Cost, Unrealized Gains, Unrealized Losses and Estimated Fair Values) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 98,528	$ 99,914
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	2,336	3,271
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	71	28
Debt Securities, Held-to-maturity, Fair Value	100,793	103,157
Tax Exempt State and Political Subdivisions General Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	72,154	73,179
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	1,928	2,524
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	15	0
Debt Securities, Held-to-maturity, Fair Value	74,067	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	8,238	8,375
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	135	256
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	7	0
Debt Securities, Held-to-maturity, Fair Value	8,366	8,631
Tax Exempt State and Political Subdivisions Lease Revenues [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,336	4,395
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	21	88
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Debt Securities, Held-to-maturity, Fair Value	4,357	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	4,599	4,649
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	68	94
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	19	3
Debt Securities, Held-to-maturity, Fair Value	4,648	4,740
Tax Exempt State and Political Subdivisions Other Revenues [Member]
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	9,201	9,316
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	184	309
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	30	25
Debt Securities, Held-to-maturity, Fair Value	$ 9,355	$ 9,600