Business Segment Data (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments	2	2
Operating Revenues	$ 31,177	$ 30,131
Operating Income	6,350	7,575
Net Income	4,494	4,441
Capital Expenditures	10,011	9,577
Assets	705,002		$ 661,140
Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	27,206	26,493
Operating Income	5,625	7,015
Net Income	3,983	4,139
Capital Expenditures	9,978	9,572
Assets	705,489		661,816
Non - Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	4,100	3,750
Operating Income	725	560
Net Income	511	302
Capital Expenditures	33	5
Assets	6,987		7,093
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(129)	$ (112)
Assets	$ (7,474)		$ (7,769)