CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
OPERATING REVENUES	$ 298,044	$ 275,058	$ 578,177	$ 547,545
OPERATING EXPENSES
Operation and maintenance	27,611	30,026	52,207	55,588
General and administrative	49,462	32,493	95,170	73,387
Depreciation and amortization	39,369	35,578	78,241	70,013
Taxes other than income taxes	22,350	18,786	45,799	41,166
Other operating (income) and expenses — net	(282)	(233)	(546)	(469)
Total operating expenses	138,510	116,650	270,871	239,685
OPERATING INCOME	159,534	158,408	307,306	307,860
OTHER EXPENSES (INCOME)
Interest expense — net	51,804	50,198	102,221	98,672
Allowance for equity funds used during construction	(8,921)	(7,464)	(16,440)	(15,013)
Other income	(480)	(189)	(741)	(438)
Other expense	1,226	431	2,381	1,615
Total other expenses (income)	43,629	42,976	87,421	84,836
INCOME BEFORE INCOME TAXES	115,905	115,432	219,885	223,024
INCOME TAX PROVISION	45,179	43,096	84,922	83,556
NET INCOME	$ 70,726	$ 72,336	$ 134,963	$ 139,468
Basic earnings per common share	$ 0.46	$ 0.47	$ 0.88	$ 0.90
Diluted earnings per common share	0.46	0.46	0.88	0.89
Dividends declared per common share	$ 0.1875	$ 0.1625	$ 0.3750	$ 0.3250