Business Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 N	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Revenues	$ 31,285	$ 32,353	$ 87,424	$ 83,300
Operating Income	10,270	10,843	24,306	21,930
Net Income	5,807	6,138	13,465	11,670
Capital Expenditures	4,363	5,312	14,585	17,886
Assets	553,146		553,146		561,726
Regulated
Segment Reporting Information [Line Items]
Revenues	27,981	29,085	77,042	74,385
Operating Income	9,685	10,417	22,699	20,798
Net Income	5,505	5,926	12,648	11,070
Capital Expenditures	4,313	5,229	14,417	17,564
Assets	555,470		555,470		560,165
Non – Regulated
Segment Reporting Information [Line Items]
Revenues	3,470	3,441	10,787	9,288
Operating Income	585	426	1,607	1,132
Net Income	302	212	817	600
Capital Expenditures	50	83	168	322
Assets	8,106		8,106		11,674
Inter-segment Elimination
Segment Reporting Information [Line Items]
Revenues	(166)	(173)	(405)	(373)
Assets	$ (10,430)		$ (10,430)		$ (10,113)