Consolidated Statements of Income and Comprehensive Income (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements of Income and Comprehensive Income
Operating revenues	$ 188,229	$ 178,444	$ 359,553	$ 338,961
Operating expenses:
Operations and maintenance	70,437	69,310	137,762	136,911
Depreciation	27,578	26,802	54,871	53,002
Amortization	1,931	3,314	3,887	6,486
Taxes other than income taxes	13,446	12,943	27,211	25,803
Total expenses	113,392	112,369	223,731	222,202
Operating income	74,837	66,075	135,822	116,759
Other expense (income):
Interest expense, net	20,106	18,504	40,049	36,934
Allowance for funds used during construction	(1,932)	(1,461)	(3,909)	(3,002)
Gain on sale of other assets	(138)	(110)	(259)	(2,039)
Income before income taxes	56,801	49,142	99,941	84,866
Provision for income taxes	19,211	19,287	32,000	33,500
Net income attributable to common shareholders	37,590	29,855	67,941	51,366
Net income attributable to common shareholders	37,590	29,855	67,941	51,366
Other comprehensive income, net of tax:
Unrealized holding gain on investments	92		96	902
Reclassification adjustment for gains reported in net income	(71)		(73)	(1,330)
Comprehensive income	$ 37,611	$ 29,855	$ 67,964	$ 50,938
Net income per common share:
Basic	$ 0.27	$ 0.22	$ 0.49	$ 0.38
Diluted	$ 0.27	$ 0.22	$ 0.49	$ 0.38
Average common shares outstanding during the period:
Basic	138,114	136,785	137,971	136,647
Diluted	138,781	137,012	138,518	136,960
Cash dividends declared per common share	$ 0.155	$ 0.145	$ 0.31	$ 0.29