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Fees Paid by Fund and Related Party Transactions - Additional Information (Detail) (USD $)
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Fees Paid and Related Party Transactions [Line Items]        
USCF Management Fee     US12NG is contractually obligated to pay USCF a fee, which is paid monthly, equal to 0.75% per annum of average daily total net assets.  
Percentage of average daily net assets 0.75%   0.75%  
Ongoing Registration Fees and Other Offering Expenses     $ 0 $ 0
Licensing fee incurred     2,120 4,211
Expenses waived 12,614 35,903 28,921 73,573
Licensing Agreements | First $1,000,000,000 of combined net assets of the funds
        
Fees Paid and Related Party Transactions [Line Items]        
Fee percentage     0.04%  
Licensing Agreements | First $1,000,000,000 of combined net assets of the funds | Maximum
        
Fees Paid and Related Party Transactions [Line Items]        
Combined assets basis for determining fee percentage 1,000,000,000   1,000,000,000  
Licensing Agreements | Combined net assets above $1,000,000,000
        
Fees Paid and Related Party Transactions [Line Items]        
Fee percentage     0.02%  
Licensing Agreements | Combined net assets above $1,000,000,000 | Minimum
        
Fees Paid and Related Party Transactions [Line Items]        
Combined assets basis for determining fee percentage 1,000,000,000   1,000,000,000  
Licensing Agreements | On and after October 20, 2011
        
Fees Paid and Related Party Transactions [Line Items]        
Fee percentage     0.015%  
Assets basis for determining fee percentage     On all net assets  
Future Period - for the year ending December 31, 2012
        
Fees Paid and Related Party Transactions [Line Items]        
Estimated directors' fees and expenses     540,000  
Estimated investor tax reporting cost     $ 75,000  
Future Period - for the year ending December 31, 2012 | Maximum
        
Fees Paid and Related Party Transactions [Line Items]        
Costs and expenses annual limit for reimbursement     0.15%