Income Taxes (Reconciliation of income tax) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income taxes
Tax expense at U.S. statutory rates									$ 2,694,000	$ 2,927,000	$ 3,209,000
State tax expense (benefit), net of federal benefit									637,000	939,000	815,000
Other adjustments against income tax expense (benefit)									44,000	934,000	236,000
Income tax provision	$ 665,000	$ 1,110,000	$ 1,250,000	$ 350,000	$ 1,450,000	$ 1,295,000	$ 1,575,000	$ 480,000	$ 3,375,000	$ 4,800,000	$ 4,260,000