CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
OPERATING REVENUES
Natural gas	$ 368,391	$ 201,051	$ 662,184	$ 407,833
Crude oil and condensate	70,226	57,466	135,881	107,447
Brokered natural gas	8,244	5,149	19,137	18,593
Other	2,819	1,991	5,763	3,920
TOTAL OPERATING REVENUES	449,680	265,657	822,965	537,793
OPERATING EXPENSES
Direct operations	36,978	29,306	68,475	56,626
Transportation and gathering	52,648	33,139	98,869	63,397
Brokered natural gas cost	6,704	4,250	15,093	16,122
Taxes other than income	11,364	10,854	23,051	29,437
Exploration	4,529	16,244	8,553	20,245
Depreciation, depletion and amortization	151,389	114,616	300,042	224,973
General and administrative	21,608	46,872	57,312	69,421
TOTAL OPERATING EXPENSES	285,220	255,281	571,395	480,221
Gain / (loss) on sale of assets	276	67,703	180	67,168
INCOME FROM OPERATIONS	164,736	78,079	251,750	124,740
Interest expense and other	16,701	18,495	32,956	35,412
Income before income taxes	148,035	59,584	218,794	89,328
Income tax expense	58,921	23,647	86,856	35,073
NET INCOME	$ 89,114	$ 35,937	$ 131,938	$ 54,255
Earnings per share
Basic (in dollars per share)	$ 0.42	$ 0.17	$ 0.63	$ 0.26
Diluted (in dollars per share)	$ 0.42	$ 0.17	$ 0.62	$ 0.26
Weighted-average shares outstanding
Basic (in shares)	210,349	209,512	210,250	209,320
Diluted (in shares)	211,745	211,158	211,492	210,974
Dividends per common share (in dollars per share)	$ 0.02	$ 0.02	$ 0.04	$ 0.04