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Additional Valuation Information - Summary of the Tiered Valuation Input Levels (Detail) - USD ($)
Sep. 30, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
United States Treasury Obligations $ 232,710,289 $ 409,384,745
Exchange-Traded Fund 79,920,275 79,818,080
Money Market Mutual Fund 17,138,872 22,398,721
Total Investments in Securities 329,769,436 511,601,546
Commodity Futures Contracts, Unrealized Appreciation (Depreciation) 3,324,712 (4,534,517)
Total Investments 333,094,148 507,067,029
Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Exchange-Traded Fund 79,920,275 79,818,080
Money Market Mutual Fund 17,138,872 22,398,721
Total Investments in Securities 97,059,147 102,216,801
Commodity Futures Contracts, Unrealized Appreciation (Depreciation) 3,324,712 (4,534,517)
Total Investments 100,383,859 97,682,284
Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
United States Treasury Obligations 232,710,289 409,384,745
Total Investments in Securities 232,710,289 409,384,745
Total Investments $ 232,710,289 $ 409,384,745