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FAIR VALUE OF FINANCIAL INSTRUMENTS (Valuation of Securities Using Fair Value Hierarchy) (Detail) - USD ($)
Mar. 31, 2016
Dec. 31, 2015
Short-Term Investments [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value $ 2,617,817,593 $ 2,468,495,664
Exchange-Traded Futures Contracts [Member] | United States [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value (96,981,140) (138,508,060)
Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value 2,617,817,593 2,468,495,664
Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value (96,981,140) (138,508,060)
Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Securities, fair value $ 0 $ 0