Summary of Significant Accounting Policies - Summary of the Tiered Valuation Input Levels (Detail) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	$ 1,848,831,568	$ 2,403,838,023
Exchange-Traded Fund	250,074,684
Money Market Mutual Fund	95,926,272	131,029,805
Total investments, at value (cost $2,194,930,838 and $2,534,934,371, respectively)	2,194,832,524	2,534,867,828
Commodity Futures Contracts	(57,836,271)	101,032,417
Total Investments	2,136,996,253	2,635,900,245
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exchange-Traded Fund	250,074,684
Money Market Mutual Fund	95,926,272	131,029,805
Total investments, at value (cost $2,194,930,838 and $2,534,934,371, respectively)	346,000,956	131,029,805
Commodity Futures Contracts	(57,836,271)	101,032,417
Total Investments	288,164,685	232,062,222
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	1,848,831,568	2,403,838,023
Total investments, at value (cost $2,194,930,838 and $2,534,934,371, respectively)	1,848,831,568	2,403,838,023
Total Investments	$ 1,848,831,568	$ 2,403,838,023