CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
OPERATING REVENUES
Natural gas	$ 293,793	$ 206,782
Crude oil and condensate	65,655	49,981
Brokered natural gas	10,893	13,444
Other	2,944	1,929
TOTAL OPERATING REVENUES	373,285	272,136
OPERATING EXPENSES
Direct operations	31,497	27,320
Transportation and gathering	46,221	30,258
Brokered natural gas cost	8,389	11,872
Taxes other than income	11,687	18,583
Exploration	4,024	4,001
Depreciation, depletion and amortization	148,653	110,357
General and administrative	35,704	22,549
TOTAL OPERATING EXPENSES	286,175	224,940
Gain / (loss) on sale of assets	(96)	(535)
INCOME FROM OPERATIONS	87,014	46,661
Interest expense and other	16,255	16,917
Income before income taxes	70,759	29,744
Income tax expense	27,935	11,426
NET INCOME	$ 42,824	$ 18,318
Earnings per share
Basic (in dollars per share)	$ 0.20	$ 0.09
Diluted (in dollars per share)	$ 0.20	$ 0.09
Weighted-average shares outstanding
Basic (in shares)	210,150	209,128
Diluted (in shares)	211,376	210,813
Dividends per common share (in dollars per share)	$ 0.02	$ 0.02