Additional Valuation Information - Summary of the Tiered Valuation Input Levels (Detail) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	$ 226,342,665	$ 409,384,745
Exchange-Traded Fund	79,935,415	79,818,080
Money Market Mutual Fund	22,018,773	22,398,721
Total Investments in Securities	328,296,853	511,601,546
Commodity Futures Contracts, Unrealized Appreciation (Depreciation)	(2,462,317)	(4,534,517)
Total Investments	325,834,536	507,067,029
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exchange-Traded Fund	79,935,415	79,818,080
Money Market Mutual Fund	22,018,773	22,398,721
Total Investments in Securities	101,954,188	102,216,801
Commodity Futures Contracts, Unrealized Appreciation (Depreciation)	(2,462,317)	(4,534,517)
Total Investments	99,491,871	97,682,284
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	226,342,665	409,384,745
Total Investments in Securities	226,342,665	409,384,745
Total Investments	$ 226,342,665	$ 409,384,745