Additional Valuation Information - Summary of the Tiered Valuation Input Levels (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	$ 1,447,699,255	$ 1,614,425,920
Exchange-Traded Fund	250,264,476	250,145,856
Money Market Mutual Fund	69,332,053	144,939,067
Total Investments in Securities	1,767,295,784	2,009,510,843
Commodity Futures Contracts, Appreciation	48,737,246	9,428,661
Commodity Futures Contracts, Depreciation	(68,565,244)	(253,228,835)
Commodity Futures Contracts	(19,827,998)	(243,800,174)
Total Investments	1,747,467,786	1,765,710,669
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exchange-Traded Fund	250,264,476	250,145,856
Money Market Mutual Fund	69,332,053	144,939,067
Total Investments in Securities	319,596,529	395,084,923
Commodity Futures Contracts, Appreciation	48,737,246	9,428,661
Commodity Futures Contracts, Depreciation	(68,565,244)	(253,228,835)
Commodity Futures Contracts	(19,827,998)	(243,800,174)
Total Investments	299,768,531	151,284,749
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	1,447,699,255	1,614,425,920
Total Investments in Securities	1,447,699,255	1,614,425,920
Total Investments	$ 1,447,699,255	$ 1,614,425,920

Financial instruments owned exchange traded fund.

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Financial instruments owned money market mutual fund at fair value.

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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.

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The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

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-Topic 940
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The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

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