Derivative Instruments - Fair Value of Derivative Instruments (Detail) - Commodity Futures Contract [Member] - Not Designated as Hedging Instrument [Member] - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Assets	$ 8,549,360	$ 4,491,410
Liabilities	$ (27,631,137)	$ (22,352,295)

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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