Acquisition - Additional Information (Detail) - Flat Castle Acquisition [Member] shares in Millions, $ in Millions	Jan. 18, 2018 USD ($) a Well shares
Business Acquisition [Line Items]
Area of land purchased \| a	44,500
Purchase price	$ 90
Purchase price paid through shares of common stock \| shares	37.8
Transaction costs capitalized related to acquisition	$ 1
Proved Oil And Gas Properties [Member]
Business Acquisition [Line Items]
Number of producing wells acquired \| Well	1
Purchase price	$ 4
Unproved Oil and Natural Gas Properties [Member]
Business Acquisition [Line Items]
Purchase price	$ 86

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

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