Business Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 N	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Operating Revenues	$ 29,102	$ 27,401	$ 56,140	$ 50,947
Operating Income	8,171	7,210	14,036	11,087
Net Income	4,481	3,725	7,658	5,532
Capital Expenditures	5,716	6,436	10,222	12,574
Assets	552,425		552,425		561,726
Regulated
Segment Reporting Information [Line Items]
Operating Revenues	25,637	24,442	49,061	45,300
Operating Income	7,678	6,878	13,016	10,381
Net Income	4,235	3,557	7,145	5,144
Capital Expenditures	5,703	6,296	10,104	12,335
Assets	551,039		551,039		560,165
Non - Regulated
Segment Reporting Information [Line Items]
Operating Revenues	3,580	3,089	7,316	5,847
Operating Income	493	332	1,020	706
Net Income	246	168	513	388
Capital Expenditures	13	140	118	239
Assets	11,444		11,444		11,674
Inter-segment Elimination
Segment Reporting Information [Line Items]
Operating Revenues	(115)	(130)	(237)	(200)
Assets	$ (10,058)		$ (10,058)		$ (10,113)