Consolidated Statements Of Operations (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements Of Operations
Operating revenues	$ 242,605	$ 211,397	$ 418,717	$ 415,565	$ 880,403	$ 849,476
Energy expenses:
Fuel	61,318	50,752	104,077	99,845	204,061	199,506
Purchased and interchanged power	16,297	19,552	34,771	48,399	78,288	99,309
Cost of services, energy services, total	77,615	70,304	138,848	148,244	282,349	298,815
Operating revenues net of energy expenses	164,990	141,093	279,869	267,321	598,054	550,661
Other operating expenses:
Other operations	57,209	51,544	111,316	101,642	233,895	217,545
Maintenance	16,760	15,735	28,996	30,235	55,584	60,066
Depreciation and amortization	19,524	20,167	40,460	39,451	82,020	78,012
Taxes other than income taxes	13,376	13,170	26,503	24,913	56,079	49,883
Utilities operating expense, total	106,869	100,616	207,275	196,241	427,578	405,506
Operating income	58,121	40,477	72,594	71,080	170,476	145,155
Other income (deductions):
Allowance for equity funds used during construction	2,011	2,707	5,062	5,247	10,631	9,346
Investment and interest income, net	1,590	840	3,975	1,938	7,352	7,387
Miscellaneous non-operating income	1	151	271	153	1,486	499
Miscellaneous non-operating deductions	(698)	(529)	(1,413)	(888)	(3,731)	(2,330)
Nonoperating income (expense), total	2,904	3,169	7,895	6,450	15,738	14,902
Interest charges (credits):
Interest on long-term debt and revolving credit facility	13,526	12,241	27,024	24,442	53,408	48,834
Other interest	237	25	534	65	723	209
Capitalized interest	(1,290)	(258)	(2,546)	(486)	(4,547)	(933)
Allowance for borrowed funds used during construction	(1,180)	(1,534)	(3,029)	(3,101)	(6,599)	(5,757)
Interest expense, total	11,293	10,474	21,983	20,920	42,985	42,353
Income before income taxes	49,732	33,172	58,506	56,610	143,229	117,704
Income tax expense	16,742	11,665	18,741	23,654	46,103	42,855
Income before extraordinary item					97,126	74,849
Extraordinary gain related to Texas regulatory assets, net of tax					10,286	0
Net income	$ 32,990	$ 21,507	$ 39,765	$ 32,956	$ 107,412	$ 74,849
Basic earnings per share:
Income before extraordinary item					$ 2.28	$ 1.70
Extraordinary gain related to Texas regulatory assets, net of tax					$ 0.24	$ 0.00
Net income	$ 0.78	$ 0.49	$ 0.94	$ 0.75	$ 2.52	$ 1.70
Diluted earnings per share:
Income before extraordinary item					$ 2.27	$ 1.69
Extraordinary gain related to Texas regulatory assets, net of tax					$ 0.24	$ 0.00
Net income	$ 0.78	$ 0.49	$ 0.94	$ 0.75	$ 2.51	$ 1.69
Dividends declared per share of common stock	$ 0.22	$ 0.00	$ 0.22	$ 0.00	$ 0.22	$ 0.00
Weighted average number of shares outstanding	41,853,552	43,460,458	42,079,568	43,598,933	42,376,298	43,943,503
Weighted average number of shares and dilutive potential shares outstanding	42,076,659	43,557,788	42,298,716	43,710,026	42,595,011	44,059,201