Additional Valuation Information - Summary of the Tiered Valuation Input Levels (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	$ 460,172,505	$ 846,158,812
Exchange-Traded Fund	79,689,390
Money Market Mutual Fund	1,322,308	3,786,312
Total Investments in Securities	541,184,203	849,945,124
Currency Futures Contracts, Depreciation	(7,972,637)
Currency Futures Contracts		1,988,810
Total Investments	533,211,566	851,933,934
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exchange-Traded Fund	79,689,390
Money Market Mutual Fund	1,322,308	3,786,312
Total Investments in Securities	81,011,698	3,786,312
Currency Futures Contracts, Depreciation	(7,972,637)
Currency Futures Contracts		1,988,810
Total Investments	73,039,061	5,775,122
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
United States Treasury Obligations	460,172,505	846,158,812
Total Investments in Securities	460,172,505	846,158,812
Total Investments	$ 460,172,505	$ 846,158,812