Acquisitions and Dispositions - Dispositions - Additional Information (Detail) - USD ($)	3 Months Ended			6 Months Ended		9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets	$ (2,597,000)		$ (681,000)			$ (7,544,000)	$ 2,053,000
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	(2,600,000)			$ (6,200,000)
Proceeds from sale of oil and gas properties	900,000			77,700,000
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
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	30,000		(681,000)	(198,000)	$ 2,700,000
Proceeds from sale of oil and gas properties	$ 131,000		$ 524,000	1,700,000	14,300,000
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
West 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					$ 10,500,000