Additional Valuation Information - Summary of the Tiered Valuation Input Levels (Detail) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	$ 2,609,081,256	$ 1,839,039,728
Exchange-Traded Fund	251,735,364	249,742,548
Money Market Mutual Fund	148,172,071	68,003,679
Total Investments in Securities	3,008,988,691	2,156,785,955
Commodity Futures Contracts, Appreciation	215,717,881	141,995,427
Commodity Futures Contracts, Depreciation	(103,124,169)	(26,326,112)
Commodity Futures Contracts	112,593,712	115,669,315
Total Investments	3,121,582,403	2,272,455,270
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exchange-Traded Fund	251,735,364	249,742,548
Money Market Mutual Fund	148,172,071	68,003,679
Total Investments in Securities	399,907,435	317,746,227
Commodity Futures Contracts, Appreciation	215,717,881	141,995,427
Commodity Futures Contracts, Depreciation	(103,124,169)	(26,326,112)
Commodity Futures Contracts	112,593,712	115,669,315
Total Investments	512,501,147	433,415,542
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	2,609,081,256	1,839,039,728
Total Investments in Securities	2,609,081,256	1,839,039,728
Total Investments	$ 2,609,081,256	$ 1,839,039,728