Derivative Instruments - Summary of Gross and Net Amounts of Offsetting Assets and Liabilities (Detail) - Currency Futures Contract [Member] - Morgan Stanley & Co. LLC [Member] - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets And Liabilities [Line Items]
Financial Derivative Assets, Futures Contracts	$ 36,772	$ 583,889
Financial Derivative Liabilities, Futures Contracts	(104,932)	(382,913)
Net value of derivatives	(68,160)	200,976
Collateral (Received)/Pledged, Non-Cash	$ 68,160
Net amount		$ 200,976

Offsetting assets and liabilities.

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Amount of right to receive securities collateral under master netting arrangements that have not been offset against derivative liabilities.

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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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