Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 90,846	$ 103,539	$ 100,603
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of electric plant in service	78,556	81,331	81,011
Amortization of nuclear fuel	42,953	37,018	31,316
Extraordinary gain related to Texas regulatory assets, net of tax	0	0	(10,286)
Deferred income taxes, net	43,561	45,688	27,456
Allowance for equity funds used during construction	(9,427)	(8,161)	(10,816)
Other amortization and accretion	14,724	19,875	16,740
Other operating activities	(479)	1,036	(881)
Change in:
Accounts receivable	13,448	(4,663)	(1,303)
Inventories	(1,926)	(3,750)	1,143
Net overcollection (undercollection) of fuel revenues	11,668	(26,001)	958
Prepayments and other	(2,784)	(2,538)	(544)
Accounts payable	1,725	4,401	(9,634)
Taxes accrued	(3,054)	11,915	18,523
Other current liabilities	78	(2,262)	1,127
Deferred charges and credits	(6,781)	(5,911)	(6,063)
Net cash provided by operating activities	273,108	251,517	239,350
Cash flows from investing activities:
Cash additions to utility property, plant and equipment	(202,387)	(178,041)	(169,966)
Cash additions to nuclear fuel	(46,009)	(39,551)	(34,277)
Capitalized interest and AFUDC:
Utility property, plant and equipment	(15,000)	(13,009)	(17,487)
Nuclear fuel	(5,312)	(5,177)	(2,487)
Allowance for equity funds used during construction	9,427	8,161	10,816
Decommissioning trust funds:
Purchases, including funding of $4.5 million, $8.3 million and $8.2 million, respectively	(107,705)	(95,441)	(73,192)
Sales and maturities	98,542	82,926	61,656
Proceeds from sale of investments in debt securities	0	2,000	0
Other investing activities	2,390	727	286
Net cash used for investing activities	(266,054)	(237,405)	(224,651)
Cash flows from financing activities:
Repurchases of common stock	0	(86,508)	(33,726)
Dividends paid	(38,889)	(27,223)	0
Pollution control bonds:
Proceeds	92,535	0	0
Payments	(92,535)	0	0
Proceeds from issuance of senior notes	149,682	0	110,000
Borrowings under the revolving credit facility:
Proceeds	234,575	120,450	37,628
Payments	(245,799)	(91,775)	(139,922)
Other financing activities	(3,774)	(32)	(1,285)
Net cash provided (used for) financing activities	95,795	(85,088)	(27,305)
Net increase (decrease) in cash and cash equivalents	102,849	(70,976)	(12,606)
Cash and cash equivalents at beginning of period	8,208	79,184	91,790
Cash and cash equivalents at end of period	$ 111,057	$ 8,208	$ 79,184