Fees Paid by Fund and Related Party Transactions (Additional Information) (Details) (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Fees Paid and Related Party Transactions [Line Items]      
USCF Management Fee USL is contractually obligated to pay USCF a fee, which is paid monthly, equal to 0.60% per annum of average daily total net assets.    
Percentage of average daily total net assets 0.60%    
Ongoing Registration Fees and Other Offering Expenses $ 81,535 $ 44,044 $ 9,472
Estimated directors' fees and expenses 10,410 14,038 17,340
Licensing fee incurred 12,774 20,192 49,913
Estimated investor tax reporting cost 150,000 150,000 200,000
USL and the Related Public Funds, other than USCI, USAG, CPER and USMI
      
Fees Paid and Related Party Transactions [Line Items]      
Estimated directors' fees and expenses 555,456 540,586 607,582
USL
      
Fees Paid and Related Party Transactions [Line Items]      
Estimated directors' fees and expenses 19,339 25,332 29,439
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    
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    
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