Business Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 N	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Operating Revenues	$ 32,669	$ 31,285	$ 89,032	$ 87,424
Operating Income	11,620	10,270	26,333	24,306
Net Income	6,758	5,807	14,654	13,465
Capital Expenditures	7,278	4,363	15,783	14,585
Assets	542,498		542,498		530,341
Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	29,346	27,981	78,719	77,042
Operating Income	11,039	9,685	24,585	22,699
Net Income	6,458	5,505	13,753	12,648
Capital Expenditures	7,211	4,313	15,685	14,417
Assets	540,970		540,970		529,381
Non - Regulated [Member]
Segment Reporting Information [Line Items]
Operating Revenues	3,492	3,470	10,752	10,787
Operating Income	581	585	1,748	1,607
Net Income	300	302	901	817
Capital Expenditures	67	50	98	168
Assets	8,262		8,262		8,887
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(169)	(166)	(439)	(405)
Assets	$ (6,734)		$ (6,734)		$ (7,927)