CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
OPERATING REVENUES
Natural gas	$ 1,405,262	$ 933,640	$ 796,517
Crude oil and condensate	291,418	227,933	125,972
Brokered natural gas	36,450	34,005	51,190
Other	13,148	8,968	6,185
TOTAL OPERATING REVENUES	1,746,278	1,204,546	979,864
OPERATING EXPENSES
Direct operations	140,856	118,243	107,409
Transportation and gathering	229,489	143,309	73,322
Brokered natural gas cost	29,936	28,502	43,834
Taxes other than income	43,045	48,874	27,576
Exploration	18,165	37,476	36,447
Depreciation, depletion and amortization	651,052	451,405	343,141
General and administrative	104,606	121,239	104,667
TOTAL OPERATING EXPENSES	1,217,149	949,048	736,396
Gain/(loss) on sale of assets	21,351	50,635	63,382
INCOME FROM OPERATIONS	550,480	306,133	306,850
Interest expense and other	64,942	68,293	71,663
Income before income taxes	485,538	237,840	235,187
Income tax expense	205,765	106,110	112,779
NET INCOME	$ 279,773	$ 131,730	$ 122,408
Earnings per share
Basic (in dollars per share)	$ 0.67	$ 0.31	$ 0.29
Diluted (in dollars per share)	$ 0.66	$ 0.31	$ 0.29
Weighted-average common shares outstanding
Basic (in shares)	420,188	419,075	416,996
Diluted (in shares)	422,375	421,987	421,522
Dividends per common share (in dollars per share)	$ 0.06	$ 0.04	$ 0.03