Dispositions and Acquisitions - Dispositions - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended								9 Months Ended	12 Months Ended
	Feb. 28, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 30, 2015
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets		$ 207,000	$ 102,000	$ 807,000	$ 22,600,000	$ 470,000	$ (2,597,000)	$ (3,304,000)	$ (1,643,000)		$ 23,716,000	$ (7,074,000)	$ (406,856,000)
Texas Panhandle Properties
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets		(989,000)
Proceeds from sale of oil and gas properties		$ 40,400,000
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										$ (5,300,000)	23,800,000
Proceeds from sale of oil and gas properties										$ 78,600,000	30,800,000
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											870,000	302,000	943,000
Proceeds from sale of oil and gas properties											$ 1,300,000	3,700,000	4,400,000
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
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)
Cash proceeds from sale of assets													$ 876,000,000
Net operating income prior to disposition														$ 52,300,000
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 properties	$ 10,500,000