CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
OPERATING REVENUES	$ 280,133	$ 272,487
OPERATING EXPENSES
Operation and maintenance	24,596	25,562
General and administrative	45,708	40,894
Depreciation and amortization	38,872	34,435
Taxes other than income taxes	23,449	22,380
Other operating (income) and expenses — net	(264)	(236)
Total operating expenses	132,361	123,035
OPERATING INCOME	147,772	149,452
OTHER EXPENSES (INCOME)
Interest expense — net	50,417	48,474
Allowance for equity funds used during construction	(7,519)	(7,549)
Other income	(268)	(253)
Other expense	1,162	1,188
Total other expenses (income)	43,792	41,860
INCOME BEFORE INCOME TAXES	103,980	107,592
INCOME TAX PROVISION	39,743	40,460
NET INCOME	$ 64,237	$ 67,132
Basic earnings per common share	$ 0.42	$ 0.43
Diluted earnings per common share	0.42	0.43
Dividends declared per common share	$ 0.1875	$ 0.1625