Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 81,918	$ 91,428	$ 88,583
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	89,824	83,342	79,626
Amortization of nuclear fuel	43,099	43,864	42,537
Deferred income taxes, net	30,846	39,129	44,678
Allowance for equity funds used during construction	(10,639)	(14,662)	(10,008)
Other amortization and accretion	17,707	18,380	16,556
Gain on sale of property, plant and equipment	(658)	(2,092)	(112)
Net gains on sale of decommissioning trust funds	(11,114)	(7,350)	(553)
Other operating activities	517	(93)	(260)
Change in:
Accounts receivable	4,839	(5,815)	(2,450)
Inventories	(2,859)	(786)	(3,673)
Net over-collection (under-collection) of fuel revenues	13,344	(3,121)	(10,843)
Prepayments and other	(3,984)	(2,750)	(4,295)
Accounts payable	(11,235)	9,684	8,180
Taxes accrued	4,512	(2,209)	(627)
Other current liabilities	3,719	1,198	958
Deferred charges and credits	(3,165)	(4,807)	(822)
Net cash provided by operating activities	246,671	243,340	247,475
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(281,458)	(277,078)	(237,411)
Cash additions to nuclear fuel	(41,966)	(37,877)	(30,535)
Capitalized interest and AFUDC:
Utility property, plant and equipment	(17,576)	(23,030)	(16,063)
Nuclear fuel	(4,968)	(5,092)	(5,299)
Allowance for equity funds used during construction	10,639	14,662	10,008
Decommissioning trust funds:
Purchases, including funding of $4.5 million	(110,223)	(117,675)	(65,491)
Sales and maturities	102,567	108,311	56,148
Proceeds from sale of property, plant, and equipment	721	2,395	112
Other investing activities	(470)	4,192	5,767
Net cash used for investing activities	(342,734)	(331,192)	(282,764)
Cash flows from financing activities:
Dividends paid	(47,059)	(44,556)	(42,049)
Borrowings under the revolving credit facility:
Proceeds	344,398	231,399	44,883
Payments	(217,192)	(231,219)	(52,686)
Payment on maturing RGRT senior notes	(15,000)	0	0
Proceeds from issuance of senior notes	0	149,468	0
Other financing activities	(1,439)	(2,328)	(324)
Net cash provided by (used for) financing activities	63,708	102,764	(50,176)
Net increase (decrease) in cash and cash equivalents	(32,355)	14,912	(85,465)
Cash and cash equivalents at beginning of period	40,504	25,592	111,057
Cash and cash equivalents at end of period	$ 8,149	$ 40,504	$ 25,592