Business Segment Data (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Operating Revenues	$ 39,874	$ 39,920	$ 109,117	$ 106,965
Operating Income	11,424	13,177	26,873	29,088
Net Income	11,476	12,737	29,305	30,118
Capital Expenditures	14,745	25,367	61,245	70,785
Assets	1,029,592		1,029,592		$ 976,470
Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	37,396	37,041	100,426	98,267
Operating Income	10,654	12,119	24,082	26,598
Net Income	10,924	11,993	27,271	28,364
Capital Expenditures	14,743	25,266	61,097	70,398
Assets	1,037,503		1,037,503		998,932
Non - Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	2,995	3,204	9,657	9,345
Operating Income	770	1,058	2,791	2,490
Net Income	552	744	2,034	1,754
Capital Expenditures	2	101	148	387
Assets	7,592		7,592		8,289
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(517)	$ (325)	(966)	$ (647)
Assets	$ (15,503)		$ (15,503)		$ (30,751)