Dispositions - Additional Information (Detail) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets	$ 156,000		$ 807,000		$ 179,000	$ 23,407,000
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	156,000	$ 23,000	1,200,000	$ 69,000
Proceeds from sale of oil and gas properties	$ 326,000	$ 40,000	$ 1,200,000	$ 53,000
Western Oklahoma Property
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets						22,100,000
Proceeds from sale of oil and gas properties						$ 26,000,000