CONDENSED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Operating Revenues	$ 68,762	$ 75,812	$ 256,528	$ 343,470
Operating Expenses:
Cost of Sales (Excluding depreciation)	19,997	25,419	89,300	171,521
Operations	22,525	23,939	48,594	57,297
Maintenance	4,259	3,928	8,643	7,926
Depreciation	11,490	9,711	22,700	19,302
Energy and Other Taxes	560	854	1,587	2,274
Total Operating Expenses	58,831	63,851	170,824	258,320
Operating Income	9,931	11,961	85,704	85,150
Other Income and Expense	1,079	1,670	1,915	2,430
Interest Charges	(4,552)	(5,113)	(9,339)	(10,303)
Income Before Income Taxes	6,458	8,518	78,280	77,277
Income Taxes	(1,415)	(3,292)	(28,819)	(29,464)
Net Income	$ 5,043	$ 5,226	$ 49,461	$ 47,813