Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 96,768	$ 81,918	$ 91,428
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	84,317	89,824	83,342
Amortization of nuclear fuel	43,748	43,099	43,864
Deferred income taxes, net	50,510	30,846	39,129
Allowance for equity funds used during construction	(7,023)	(10,639)	(14,662)
Other amortization and accretion	17,295	17,707	18,380
Gain on sale of property, plant and equipment	(545)	(658)	(2,092)
Net gains on sale of decommissioning trust funds	(7,640)	(11,114)	(7,350)
Other operating activities	1,279	517	(93)
Change in:
Accounts receivable	(17,511)	4,839	(5,815)
Inventories	265	(2,859)	(786)
Net over-collection (under-collection) of fuel revenues	(14,891)	13,344	(3,121)
Prepayments and other	(1,184)	(3,984)	(2,750)
Accounts payable	(2,140)	(11,235)	9,684
Taxes accrued	1,945	4,512	(2,209)
Other current liabilities	2,022	3,719	1,198
Deferred charges and credits	(16,065)	(3,165)	(4,807)
Net cash provided by operating activities	231,150	246,671	243,340
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(225,361)	(281,458)	(277,078)
Cash additions to nuclear fuel	(42,383)	(41,966)	(37,877)
Capitalized interest and AFUDC:
Utility property, plant and equipment	(12,006)	(17,576)	(23,030)
Nuclear fuel	(4,990)	(4,968)	(5,092)
Allowance for equity funds used during construction	7,023	10,639	14,662
Decommissioning trust funds:
Purchases, including funding of $4.5 million	(99,497)	(110,223)	(117,675)
Sales and maturities	91,268	102,567	108,311
Proceeds from sale of property, plant, and equipment	4,841	721	2,395
Other investing activities	5,373	(470)	4,192
Net cash used for investing activities	(275,732)	(342,734)	(331,192)
Cash flows from financing activities:
Dividends paid	(49,603)	(47,059)	(44,556)
Borrowings under the revolving credit facility:
Proceeds	355,607	344,398	231,399
Payments	(415,771)	(217,192)	(231,219)
Payment on maturing RGRT senior notes	0	(15,000)	0
Proceeds from issuance of senior notes	157,052	0	149,468
Other financing activities	(2,432)	(1,439)	(2,328)
Net cash provided by financing activities	44,853	63,708	102,764
Net increase (decrease) in cash and cash equivalents	271	(32,355)	14,912
Cash and cash equivalents at beginning of period	8,149	40,504	25,592
Cash and cash equivalents at end of period	$ 8,420	$ 8,149	$ 40,504