Acquisitions and Dispositions - Additional Information (Detail) - USD ($)	1 Months Ended			3 Months Ended								6 Months Ended		10 Months Ended	12 Months Ended
	Feb. 28, 2015	Apr. 30, 2014	Apr. 30, 2013	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Jun. 16, 2014	Nov. 01, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets				$ (408,909,000)	$ (681,000)	$ 2,909,000	$ (175,000)	$ 3,760,000	$ 167,000	$ 282,064,000	$ (353,000)				$ (406,856,000)	$ 285,638,000	$ 92,291,000
Conger Exchange Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets										$ 280,100,000
Cash proceeds from sale of assets		$ 145,000,000
Net operating income prior to disposition												$ 25,700,000	$ 21,900,000				48,700,000
Gain on sale of assets after selling expenses																272,700,000
Sale and exchange transaction, closing date															Jun. 16, 2014
Selling expenses for property sale																$ 5,000,000
Recognized revenue from sale of property interests acquire												$ 33,800,000
Nora Gathering, LLC
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Percentage of ownership interest, acquired								50.00%				50.00%				50.00%
Percentage ownership interest								50.00%				50.00%				50.00%
Fair value of membership interest on acquisition date																$ 134,800,000
Nora Gathering, LLC | Conger Exchange Transaction
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain on fair value of membership interest																10,000,000
Virginia And West Virginia Property
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets				$ (407,700,000)											$ (407,700,000)
Cash proceeds from sale of assets															876,000,000
Net operating income prior to disposition														$ 52,300,000		98,300,000	46,100,000
West Texas Properties
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets	$ (101,000)
Proceeds from sale of oil and gas	$ 10,500,000
Miscellaneous Proved, Unproved Properties and Surface Acreage
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets															943,000	3,000,000	13,200,000
Proceeds from sale of oil and gas															$ 4,400,000	$ 35,500,000	$ 40,500,000
Delaware and Permian Basin
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets			$ 83,300,000
Proceeds from sale of oil and gas			275,000,000
Selling expenses for property sale			$ 4,200,000