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FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS (Additional Information) (Details) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2017
Fees Paid and Related Party Transactions [Line Items]            
USCF Management Fee       UNL is contractually obligated to pay USCF a fee, which is paid monthly, equal to 0.75% per annum of average daily total net assets.    
Estimated directors fees and expenses   $ 500 $ 411 $ 1,432 $ 2,469  
Licensing fee incurred   356 541 1,254 1,477  
Expense waiver (Note 3)   $ 19,588 $ 28,986 $ 44,548 $ 76,717  
Licensing Agreements [Member]            
Fees Paid and Related Party Transactions [Line Items]            
Fee percentage       0.015%    
Future Period - for the year ending December 31, 2017 [Member] | Subsequent Event [Member]            
Fees Paid and Related Party Transactions [Line Items]            
Estimated investor tax reporting cost $ 65,000          
Future Period - for the year ending December 31, 2017 [Member] | Maximum [Member]            
Fees Paid and Related Party Transactions [Line Items]            
Costs and expenses annual limit for reimbursement       0.15%    
UNL [Member] | Scenario, Forecast [Member]            
Fees Paid and Related Party Transactions [Line Items]            
Estimated directors fees and expenses           $ 1,700
UNL [Member] | Related Public Funds [Member] | Scenario, Forecast [Member]            
Fees Paid and Related Party Transactions [Line Items]            
Estimated directors fees and expenses           $ 539,350