Summary of Significant Accounting Policies - Schedule of Derivative Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Assets, Fair Value	$ 55,426	$ 75,304
Assets, Fair Value	5,045	13,888
Liability, Fair Value	11,765	222
Liability, Fair Value	13,058	4,220
Derivative Financial Instruments – current
Derivative [Line Items]
Assets, Fair Value	55,426	75,304
Liability, Fair Value	11,765	222
Derivative Financial Instruments – long-term
Derivative [Line Items]
Liability, Fair Value	13,058	4,220
Natural Gas Derivatives \| Derivative Financial Instruments – current
Derivative [Line Items]
Assets, Fair Value	49,793	75,123
Liability, Fair Value	10,849
Natural Gas Derivatives \| Derivative Financial Instruments – long-term
Derivative [Line Items]
Assets, Fair Value	5,045	13,888
Liability, Fair Value	11,160	4,220
Oil Price Derivatives \| Derivative Financial Instruments – current
Derivative [Line Items]
Assets, Fair Value	5,633	181
Liability, Fair Value		$ 222
Interest Rate Derivatives \| Derivative Financial Instruments – current
Derivative [Line Items]
Liability, Fair Value	916
Interest Rate Derivatives \| Derivative Financial Instruments – long-term
Derivative [Line Items]
Liability, Fair Value	$ 1,898

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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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