STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Gross Margin
Revenues	$ 550,408	$ 508,364
Cost of natural gas	263,154	235,729
Net margin	287,254	272,635
Operating expenses
Operations and maintenance	109,357	106,131
Depreciation and amortization	37,019	34,684
General taxes	15,746	15,747
Total operating expenses	162,122	156,562
Operating income	125,132	116,073
Other income	1,246	18
Other expense	(340)	(455)
Interest expense, net	(11,481)	(10,847)
Income before income taxes	114,557	104,789
Income taxes	(38,101)	(40,046)
Net income	$ 76,456	$ 64,743
Earnings per share
Basic	$ 1.45	$ 1.23
Diluted	$ 1.44	$ 1.22
Average shares (thousands)
Basic	52,576	52,519
Diluted	53,056	53,107
Dividends declared per share of stock	$ 0.42	$ 0.35