CONDENSED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Operating Revenues	$ 66,536	$ 59,177	$ 240,634	$ 238,613
Operating Expenses:
Cost of Sales (Excluding depreciation)	26,108	20,407	103,710	106,906
Operations	19,468	18,577	43,519	39,141
Maintenance	3,365	3,371	6,787	6,563
Depreciation	8,249	7,878	16,474	15,035
Energy and Other Taxes	1,277	1,479	4,280	4,648
Total Operating Expenses	58,467	51,712	174,770	172,293
Operating Income	8,069	7,465	65,864	66,320
Other Income and Expense	810	1,430	2,260	2,779
Interest Charges	(2,789)	(3,771)	(5,750)	(7,960)
Income Before Income Taxes	6,090	5,124	62,374	61,139
Income Taxes	(2,269)	(1,887)	(23,040)	(22,864)
Net Income	$ 3,821	$ 3,237	$ 39,334	$ 38,275