Summary of Significant Accounting Policies - Schedule of Derivative Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Net Fair Value Presented in the Consolidated Balance Sheet, Asset Derivatives - current	$ 2,356	$ 15,401
Derivative Financial Instruments – Current \| Natural Gas Price Derivatives
Derivative [Line Items]
Asset Derivatives, Fair Value	4,075	7,264
Gross Amounts Offset in the Consolidated Balance Sheet, Assets Derivatives	(964)	(1,168)
Net Fair Value Presented in the Consolidated Balance Sheet, Asset Derivatives - current	3,111	6,096
Liability Derivatives, Fair Value	964	1,168
Gross Amounts Offset in the Consolidated Balance Sheet, Liabilities Derivatives	(964)	(1,168)
Derivative Financial Instruments – Current \| Oil Price Derivatives
Derivative [Line Items]
Asset Derivatives, Fair Value	535	9,305
Gross Amounts Offset in the Consolidated Balance Sheet, Assets Derivatives	(1,290)
Net Fair Value Presented in the Consolidated Balance Sheet, Asset Derivatives - current	(755)	$ 9,305
Liability Derivatives, Fair Value	1,290
Gross Amounts Offset in the Consolidated Balance Sheet, Liabilities Derivatives	$ (1,290)

Derivative assets offset in balance sheet.

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- Definition

Derivative liabilities offset in balance sheet.

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No definition available.

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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.

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Fair value, before 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. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, before effects of master netting arrangements, of a financial liability or 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. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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