Derivative Instruments - Summary of Average Monthly Notional Value of Future Contracts Outstanding (Detail) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Weighted Average [Member] \| Commodity Futures Contract [Member]
Derivative [Line Items]
Average Notional Value	$ 1,500,591,832	$ 2,703,938,751	$ 1,689,903,075	$ 2,716,432,711

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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