Dispositions and Acquisitions - Dispositions - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets	$ (10,815,000)	$ (30,000)	$ 156,000	$ 23,000	$ 207,000	$ 102,000	$ 807,000	$ 22,600,000	$ (10,666,000)	$ 23,716,000	$ (7,074,000)
Northern Oklahoma
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets		(39,000)
Proceeds from sale of oil and gas properties		$ 23,300,000
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									(448,000)	870,000	302,000
Proceeds from sale of oil and gas properties									$ 1,200,000	1,300,000	3,700,000
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										23,800,000	(5,300,000)
Proceeds from sale of oil and gas properties										$ 30,800,000	78,600,000
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
Pennsylvania
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
(Loss) gain on the sale of assets	$ (10,200,000)
Percentage of royalty disposed	1.00%								1.00%
Proceeds from leases	$ 300,000,000