Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 84,315	$ 98,261	$ 96,768
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	96,382	90,843	84,317
Amortization of nuclear fuel	38,176	42,476	43,748
Deferred income taxes, net	29,118	49,394	50,510
Allowance for equity funds used during construction	(3,453)	(3,025)	(7,023)
Other amortization and accretion	20,830	18,954	17,295
Gain on sale of property, plant and equipment	0	0	(545)
Net losses (gains) on decommissioning trust funds	12,967	(10,626)	(7,640)
Other operating activities	(38)	(692)	1,279
Change in:
Accounts receivable	5,712	(138)	(17,511)
Inventories	(4,117)	(3,073)	265
Prepayments and other	(4,419)	(692)	(1,184)
Accounts payable	(2,233)	1,407	(2,140)
Taxes accrued	(5,487)	1,840	1,945
Interest accrued	4,008	(817)	638
Net over-collection (under-collection) of fuel revenues	4,822	17,093	(14,891)
Other current liabilities	9,289	(100)	1,384
Deferred charges and credits	(475)	(12,544)	(16,065)
Net cash provided by operating activities	285,397	288,561	231,150
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(240,021)	(199,896)	(229,722)
Cash additions to nuclear fuel	(38,354)	(38,481)	(42,383)
Insurance proceeds received for equipment	5,351	9,591	4,361
Capitalized interest and AFUDC:
Utility property, plant and equipment	(7,065)	(6,000)	(12,006)
Nuclear Fuel and other	(5,483)	(5,022)	(4,990)
Allowance for equity funds used during construction	3,453	3,025	7,023
Decommissioning trust funds:
Purchases, including funding of $2.1 million, $3.8 million and $4.5 million, respectively	(86,366)	(102,920)	(99,497)
Sales and maturities	80,732	97,037	91,268
Proceeds from sale of property, plant, and equipment	287	281	4,841
Other investing activities	4,186	(1,559)	5,373
Net cash used for investing activities	(283,280)	(243,944)	(275,732)
Cash flows from financing activities:
Dividends paid	(57,539)	(53,337)	(49,603)
Borrowings under the revolving credit facility:
Proceeds	567,894	638,458	355,607
Payments	(692,220)	(546,499)	(415,771)
Other financing activities	(4,342)	(1,369)	(2,432)
Net cash provided by (used for) financing activities	3,793	(46,047)	44,853
Net increase (decrease) in cash and cash equivalents	5,910	(1,430)	271
Cash and cash equivalents at beginning of period	6,990	8,420	8,149
Cash and cash equivalents at end of period	12,900	6,990	8,420
4.22% Senior Notes, due 2028
Cash flows from financing activities:
Proceeds from issuance of senior notes	125,000	0	157,052
4.07% RGRT Senior Notes, due 2025
Cash flows from financing activities:
Proceeds from issuance of senior notes	65,000	0	0
4.47% Senior Notes, Series B, due 2017
Cash flows from financing activities:
Payments on maturing RGRT senior notes	0	(50,000)	0
1.875% 2012 Series A Refunding Bonds, due 2032
Cash flows from financing activities:
Payments on maturing pollution control bond	$ 0	$ (33,300)	$ 0