Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 98,261	$ 96,768	$ 81,918
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	90,843	84,317	89,824
Amortization of nuclear fuel	42,476	43,748	43,099
Deferred income taxes, net	49,394	50,510	30,846
Allowance for equity funds used during construction	(3,025)	(7,023)	(10,639)
Other amortization and accretion	18,954	17,295	17,707
Gain on sale of property, plant and equipment	0	(545)	(658)
Net gains on sale of decommissioning trust funds	(10,626)	(7,640)	(11,114)
Other operating activities	(692)	1,279	517
Change in:
Accounts receivable	(138)	(17,511)	4,839
Inventories	(3,073)	265	(2,859)
Net over-collection (under-collection) of fuel revenues	17,093	(14,891)	13,344
Prepayments and other	(692)	(1,184)	(3,984)
Accounts payable	1,407	(2,140)	(11,235)
Taxes accrued	1,840	1,945	4,512
Other current liabilities	(917)	2,022	3,719
Deferred charges and credits	(12,544)	(16,065)	(3,165)
Net cash provided by operating activities	288,561	231,150	246,671
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(190,305)	(225,361)	(281,458)
Cash additions to nuclear fuel	(38,481)	(42,383)	(41,966)
Capitalized interest and AFUDC:
Utility property, plant and equipment	(6,000)	(12,006)	(17,576)
Nuclear fuel and other	(5,022)	(4,990)	(4,968)
Allowance for equity funds used during construction	3,025	7,023	10,639
Decommissioning trust funds:
Purchases, including funding of $3.8 million, $4.5 million and $4.5 million, respectively	(102,920)	(99,497)	(110,223)
Sales and maturities	97,037	91,268	102,567
Proceeds from sale of property, plant, and equipment	281	4,841	721
Other investing activities	(1,559)	5,373	(470)
Net cash used for investing activities	(243,944)	(275,732)	(342,734)
Cash flows from financing activities:
Dividends paid	(53,337)	(49,603)	(47,059)
Borrowings under the revolving credit facility:
Proceeds	638,458	355,607	344,398
Payments	(546,499)	(415,771)	(217,192)
Payment on maturing RGRT senior notes	(50,000)	0	(15,000)
Payment on maturing of pollution control bond	(33,300)	0	0
Proceeds from issuance of senior notes	0	157,052	0
Other financing activities	(1,369)	(2,432)	(1,439)
Net cash provided by (used for) financing activities	(46,047)	44,853	63,708
Net increase (decrease) in cash and cash equivalents	(1,430)	271	(32,355)
Cash and cash equivalents at beginning of period	8,420	8,149	40,504
Cash and cash equivalents at end of period	$ 6,990	$ 8,420	$ 8,149