Significant Customers and Other Concentrations - Additional Information (Detail)	12 Months Ended
Dec. 31, 2018 counterparty Customer	Dec. 31, 2017 Customer	Dec. 31, 2016 Customer
Concentration Risk [Line Items]
Counterparties With Hedges In Place Number \| counterparty	8
Sales Revenue, Product Line [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Customers account for production revenues \| Customer	4	3	3

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.

No definition available.

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