Business Segment Data (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Operating Revenues	$ 39,920	$ 37,769	$ 106,965	$ 101,859
Operating Income	13,177	11,983	29,088	27,962
Net Income	12,737	11,119	30,118	25,818
Capital Expenditures	25,367	25,522	70,785	61,220
Assets	959,834		959,834		$ 909,878
Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	37,040	35,000	98,266	93,342
Operating Income	12,119	11,001	26,598	24,937
Net Income	11,993	10,409	28,364	23,700
Capital Expenditures	25,266	25,437	70,398	60,998
Assets	959,494		959,494		910,081
Non - Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,204	3,020	9,345	9,032
Operating Income	1,058	982	2,490	3,025
Net Income	744	710	1,754	2,118
Capital Expenditures	101	85	387	222
Assets	10,104		10,104		9,686
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(324)	$ (251)	(646)	$ (515)
Assets	$ (9,764)		$ (9,764)		$ (9,889)