Selected Quarterly Financial Data (Unaudited) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								9 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information [Line Items]
(Loss) gain on the sale of assets	$ 470	$ (2,597)	$ (3,304)	$ (1,643)	$ (408,909)	$ (681)	$ 2,909	$ (175)			$ (7,074)	$ (406,856)	$ 285,638
Impairment of proved properties and other	$ 0	$ 0	$ 0	43,040	87,941	502,233	$ 0	$ 0			$ 43,040	590,174	$ 28,024
Virginia And West Virginia Property
Selected Quarterly Financial Information [Line Items]
(Loss) gain on the sale of assets					(407,700)							$ (407,700)
Western Oklahoma Properties
Selected Quarterly Financial Information [Line Items]
(Loss) gain on the sale of assets										$ (5,300)
Impairment of proved properties and other				$ 43,000
Northern Oklahoma and Legacy Shallow Northwest Pennsylvania Assets
Selected Quarterly Financial Information [Line Items]
Impairment of proved properties and other						$ 502,200
Texas Panhandle And South Texas
Selected Quarterly Financial Information [Line Items]
Impairment of proved properties and other					$ 87,900
MRD
Selected Quarterly Financial Information [Line Items]
Impairment of proved properties and other									$ 37,200