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Summary of Significant Accounting Policies - Fair Value of Derivative Instruments (Detail) - Commodity Currency Contract [Member] - USD ($)
Mar. 31, 2017
Dec. 31, 2016
Derivatives, Fair Value [Line Items]    
Assets $ 528,539 $ 134,300
Liabilities (503,883)  
Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Assets $ 528,539 $ 112,424