Derivative Instruments - Summary of Gross and Net Amounts of Offsetting Assets and Liabilities (Detail) - Commodity Futures Contract [Member] - Morgan Stanley & Co. LLC [Member] - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets And Liabilities [Line Items]
Financial Derivative Assets	$ 353,581	$ 31,489,170
Financial Derivative Liabilities	(20,127,156)
Net value of derivatives	(19,773,575)	31,489,170
Collateral (Received)/Pledged, Non-Cash	$ 19,773,575
Net amount		$ 31,489,170

Offsetting assets and liabilities.

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Amount of obligation to return securities collateral under master netting arrangements that have not been offset against derivative assets.

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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, after offset of derivative liability, of 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, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, after effects of master netting arrangements, of 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 offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset.

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