CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
OPERATING REVENUES	$ 238,782	$ 214,801	$ 685,903	$ 608,889
OPERATING EXPENSES
Operation and maintenance	29,725	31,544	83,906	90,314
General and administrative	31,902	27,906	110,767	78,791
Depreciation and amortization	29,802	27,466	87,583	78,453
Taxes other than income taxes	16,728	14,721	49,492	44,186
Other operating (income) and expenses — net	(197)	(190)	(542)	(586)
Total operating expenses	107,960	101,447	331,206	291,158
OPERATING INCOME	130,822	113,354	354,697	317,731
OTHER EXPENSES (INCOME)
Interest expense — net	44,062	38,924	123,527	116,918
Allowance for equity funds used during construction	(8,290)	(5,622)	(25,315)	(15,800)
Other income	(786)	(884)	(824)	(2,171)
Other expense	2,164	1,415	5,388	2,473
Total other expenses (income)	37,150	33,833	102,776	101,420
INCOME BEFORE INCOME TAXES	93,672	79,521	251,921	216,311
INCOME TAX PROVISION	34,688	28,338	95,352	76,691
NET INCOME	$ 58,984	$ 51,183	$ 156,569	$ 139,620
Basic earnings per common share	$ 1.12	$ 0.99	$ 2.99	$ 2.72
Diluted earnings per common share	$ 1.12	$ 0.98	$ 2.96	$ 2.68
Dividends declared per common share	$ 0.4250	$ 0.3775	$ 1.1800	$ 1.0825