Acquisitions and Dispositions - Dispositions - Additional Information (Detail) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets	$ 807,000		$ (3,304,000)		$ 23,407,000	$ (4,947,000)
Western Oklahoma Properties
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets			(2,700,000)		22,100,000
Proceeds from sale of oil and gas properties			77,700,000		$ 26,000,000
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	1,200,000	$ 69,000	(640,000)	$ 443,000
Proceeds from sale of oil and gas properties	$ 1,200,000	$ 53,000	$ 74,000	1,600,000
Northeast Pennsylvania Non-operated Interest
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets				(2,100,000)
Proceeds from sale of oil and gas properties				111,500,000
Mississippi and South Texas properties
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from sale of oil and gas properties				$ 1,200,000