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Organization and Business - Additional Information (Detail) (USD $)
 1 Months Ended
Nov. 30, 2009
PartnershipUnit
Nov. 18, 2009
Jun. 30, 2012
PartnershipUnit
Dec. 31, 2011
Jun. 30, 2011
Dec. 31, 2010
Feb. 29, 2012
Creation Baskets
Feb. 29, 2012
Prior to February 29, 2012
Creation Baskets
Jun. 30, 2012
Open Cleared Swap and Futures Contracts
Open Futures Contracts, Long
United States
Contract
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]                  
Number of contracts                 1,242
Number of units per basket             50,000 100,000  
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets     350   1,000        
Number of initially registered units on Form S-1 with the U.S. Securities and Exchange Commission 30,000,000                
Net asset value per unit   $ 50.00 $ 17.38 $ 21.21 $ 32.57 $ 35.02      
Number of units issued   200,000              
Value of unit issued   $ 10,000,000              
Commenced investment operations date   Nov. 18, 2009              
Number of registered units     30,000,000