Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Type (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Oil And Gas Revenue [Line Items]
Total revenues	$ 130,123	$ 91,549	$ 343,938	$ 279,602
Natural Gas Sales [Member]
Oil And Gas Revenue [Line Items]
Total revenues	65,756	65,970	178,648	187,280
NGL Sales [Member]
Oil And Gas Revenue [Line Items]
Total revenues	25,074	13,741	63,520	41,954
Oil Sales [Member]
Oil And Gas Revenue [Line Items]
Total revenues	36,349	$ 11,838	98,452	47,940
Brokered Natural Gas and Marketing Revenue [Member]
Oil And Gas Revenue [Line Items]
Total revenues	$ 2,944		$ 3,318	$ 2,428

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Balance Type:	credit
Period Type:	duration