STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Gross Margin
Revenues	$ 279,689	$ 245,923	$ 830,097	$ 754,288
Cost of natural gas	82,572	56,457	345,726	292,186
Net margin	197,117	189,466	484,371	462,102
Operating expenses
Operations and maintenance	101,241	97,119	210,598	203,250
Depreciation and amortization	37,851	35,565	74,870	70,249
General taxes	13,973	13,161	29,719	28,908
Total operating expenses	153,065	145,845	315,187	302,407
Operating income	44,052	43,621	169,184	159,695
Other income	875	416	2,121	434
Other expense	(462)	(314)	(802)	(769)
Interest expense, net	(11,305)	(10,848)	(22,786)	(21,695)
Income before income taxes	33,160	32,875	147,717	137,665
Income taxes	(12,537)	(12,575)	(50,638)	(52,621)
Net income	$ 20,623	$ 20,300	$ 97,079	$ 85,044
Earnings per share
Basic	$ 0.39	$ 0.39	$ 1.85	$ 1.62
Diluted	$ 0.39	$ 0.38	$ 1.83	$ 1.61
Average shares (thousands)
Basic	52,553	52,386	52,565	52,452
Diluted	52,969	52,836	53,012	52,972
Dividends declared per share of stock	$ 0.42	$ 0.35	$ 0.84	$ 0.70