Business Segment Data (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Operating Revenues	$ 36,701	$ 35,277	$ 69,242	$ 67,046
Operating Income	9,814	9,385	15,448	15,912
Net Income	10,923	9,713	17,828	17,381
Capital Expenditures	24,467	20,270	46,500	45,417
Assets	1,014,975		1,014,975		$ 976,470
Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	33,609	32,289	63,030	61,226
Operating Income	8,711	8,639	13,427	14,480
Net Income	10,108	9,192	16,347	16,371
Capital Expenditures	24,391	19,913	46,354	44,882
Assets	1,022,776		1,022,776		998,932
Non - Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,405	3,180	6,662	6,141
Operating Income	1,103	746	2,021	1,432
Net Income	815	521	1,481	1,010
Capital Expenditures	76	357	146	535
Assets	8,459		8,459		8,289
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(313)	$ (192)	(450)	$ (321)
Assets	$ (16,260)		$ (16,260)		$ (30,751)