Divestitures (Details) (USD $)	12 Months Ended				1 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2013	Jun. 30, 2012 Pearsall shale	May 31, 2011 Haynesville/Bossier Shale Joint Ventures	Dec. 31, 2011 Haynesville/Bossier Shale Joint Ventures item	Oct. 31, 2011 Colorado, Utah and Wyoming properties	Dec. 31, 2013 Other properties	Dec. 31, 2012 Other properties	Dec. 31, 2011 Other properties	Dec. 31, 2012 Texas oil and gas properties	Dec. 31, 2013 Oklahoma and Texas panhandles oil and gas properties	Dec. 31, 2013 Oklahoma, Texas and Kansas
Significant Acquisitions and Disposals
Net Gain (loss) on sale of assets	$ 21,351,000	$ 50,635,000	$ 63,382,000		$ 67,000,000	$ 34,200,000		$ 4,200,000	$ 19,500,000	$ 1,800,000	$ 25,000,000	$ (18,200,000)	$ 19,400,000	$ (17,500,000)
Proceeds from sale of oil and gas properties before closing adjustments								285,000,000				29,900,000	160,000,000	123,400,000
Proceeds from sale of oil and gas properties deposited				28,300,000
Non-operated working interest (as a percent)					35.00%
Total consideration received from the sale of properties					251,000,000					14,400,000
Proceeds from sale of oil and gas properties					125,000,000	47,000,000			44,300,000		73,500,000
Percentage of fund for the Company's share of future drilling and completion costs					85.00%
Future drilling and completion costs to be funded by third party					125,000,000
Participation agreements							2
Third party reimbursement percentage of drilling costs							100.00%
Third party percentage of working interest in leaseholds							75.00%
Reimbursement of drilling costs by third parties							$ 12,900,000