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CONTRACTS AND AGREEMENTS (Brokerage Commission) (Detail) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Brokerage commissions $ 6,875,314 $ 5,196,820 $ 988,505
Commission [Member]      
Brokerage commissions $ 6,875,314 $ 5,196,820 $ 988,505
Percentage of average daily net assets 0.20% 0.20% 0.14%
Rebalancing Investments Transaction [Member]      
Brokerage commissions $ 6,297,055 $ 4,288,005 $ 685,780
Percentage of average daily net assets 91.59% 82.51% 69.38%
Creation And Redemption Activity [Member]      
Brokerage commissions $ 578,259 $ 908,815 $ 302,725
Percentage of average daily net assets 8.41% 17.49% 30.62%