Statements of Consolidated Income (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Operating revenues	$ 336,720	$ 257,335	$ 1,141,391	$ 951,490
Operating expenses:
Purchased gas costs	8,197	8,838	127,870	138,769
Operation and maintenance	35,872	40,483	91,513	110,775
Production	24,908	16,010	60,784	49,163
Exploration	814	941	3,387	3,354
Selling, general and administrative	44,745	34,333	124,572	117,961
Depreciation, depletion and amortization	87,343	68,548	247,627	195,644
Total operating expenses	201,879	169,153	655,753	615,666
Operating income	134,841	88,182	485,638	335,824
Gain on dispositions	180,143		202,928
Other income	3,098	2,924	27,948	8,551
Interest expense	32,503	33,861	98,642	102,075
Income before income taxes	285,579	57,245	617,872	242,300
Income taxes	106,665	20,723	228,949	87,713
Net income	$ 178,914	$ 36,522	$ 388,923	$ 154,587
Basic:
Weighted average common shares outstanding (in shares)	149,441	149,133	149,373	143,048
Net income (in dollars per share)	$ 1.20	$ 0.24	$ 2.60	$ 1.08
Diluted:
Weighted average common shares outstanding (in shares)	150,301	149,775	150,144	143,806
Net income (in dollars per share)	$ 1.19	$ 0.24	$ 2.59	$ 1.07
Dividends declared per common share (in dollars per share)	$ 0.22	$ 0.22	$ 0.66	$ 0.66