Summary of Significant Accounting Policies - Schedule of Derivative Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Asset Derivative Financial Instruments:
Derivative Financial Instruments – current	$ 8,830	$ 75,304
Derivative Financial Instruments – long-term	1,185	13,888
Liability Derivative Financial Instruments:
Derivative Financial Instruments – current	63,595	222
Derivative Financial Instruments – long-term	66,373	4,220
Derivative Financial Instruments – current
Asset Derivative Financial Instruments:
Derivative Financial Instruments – current	8,830	75,304
Liability Derivative Financial Instruments:
Derivative Financial Instruments – current	63,595	222
Derivative Financial Instruments – long-term
Liability Derivative Financial Instruments:
Derivative Financial Instruments – long-term	66,373	4,220
Natural gas price derivatives \| Derivative Financial Instruments – current
Asset Derivative Financial Instruments:
Derivative Financial Instruments – current	6,405	75,123
Liability Derivative Financial Instruments:
Derivative Financial Instruments – current	62,652	0
Natural gas price derivatives \| Derivative Financial Instruments – long-term
Asset Derivative Financial Instruments:
Derivative Financial Instruments – long-term	1,185	13,888
Liability Derivative Financial Instruments:
Derivative Financial Instruments – long-term	64,814	4,220
Oil price derivatives \| Derivative Financial Instruments – current
Asset Derivative Financial Instruments:
Derivative Financial Instruments – current	2,425	181
Liability Derivative Financial Instruments:
Derivative Financial Instruments – current	0	222
Oil price derivatives \| Derivative Financial Instruments – long-term
Liability Derivative Financial Instruments:
Derivative Financial Instruments – long-term	20	0
Interest rate derivatives \| Derivative Financial Instruments – current
Liability Derivative Financial Instruments:
Derivative Financial Instruments – current	943	0
Interest rate derivatives \| Derivative Financial Instruments – long-term
Liability Derivative Financial Instruments:
Derivative Financial Instruments – long-term	$ 1,539	$ 0

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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