Business Segment Data (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segments	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segments			2
Operating Revenues	$ 34,654	$ 32,669	$ 95,100	$ 89,032
Operating Income	11,460	11,620	27,378	26,333
Net Income	6,743	6,758	15,467	14,654
Capital Expenditures	6,651	7,278	19,297	15,783
Assets	603,079		603,079		$ 575,772
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(116)	(169)	(343)	(439)
Assets	(4,364)		(4,364)		(6,334)
Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	31,120	29,346	83,998	78,719
Operating Income	10,938	11,039	25,774	24,585
Net Income	6,466	6,458	14,653	13,753
Capital Expenditures	6,613	7,211	19,232	15,685
Assets	600,452		600,452		574,854
Non - Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,650	3,492	11,445	10,752
Operating Income	522	581	1,604	1,748
Net Income	277	300	814	901
Capital Expenditures	38	$ 67	65	$ 98
Assets	$ 6,991		$ 6,991		$ 7,252