XML 50 R27.htm IDEA: XBRL DOCUMENT v2.4.1.9
FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) (USD $)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Sep. 30, 2013
Nov. 18, 2009
Per Unit Operating Performance:        
Net asset value, beginning of period $ 13.69unl_NetAssetValuePerUnit $ 18.32unl_NetAssetValuePerUnit   $ 50.00unl_NetAssetValuePerUnit
Total income (loss) $ (1.06)unl_TotalIncomeLossPerUnit $ 1.36unl_TotalIncomeLossPerUnit    
Net expenses $ (0.03)unl_TotalExpensesPerUnit $ (0.05)unl_TotalExpensesPerUnit    
Net decrease in net asset value $ (1.09)unl_IncreaseDecreaseInNetAssetValuePerUnit $ 1.31unl_IncreaseDecreaseInNetAssetValuePerUnit    
Net asset value, end of period $ 12.60unl_NetAssetValuePerUnit $ 19.63unl_NetAssetValuePerUnit   $ 50.00unl_NetAssetValuePerUnit
Total Return (7.96%)unl_RateOfReturnOnAverageAsset   7.15%unl_RateOfReturnOnAverageAsset  
Ratios to Average Net Assets        
Total income (loss) (7.42%)unl_PercentageOfTotalRevenue 8.92%unl_PercentageOfTotalRevenue    
Management fees 0.75%unl_ManagementIncentiveFeePercentage [1] 0.75%unl_ManagementIncentiveFeePercentage [1]    
Total expenses excluding management fees 0.57%unl_ExpensesExcludingManagementFeePercentage [1] 0.87%unl_ExpensesExcludingManagementFeePercentage [1]    
Expenses waived (0.41%)unl_PercentageWaiverExpense [1] (0.64%)unl_PercentageWaiverExpense [1]    
Net expenses excluding management fees 0.16%unl_ExpenseExcludingManagementFeePercentageNet [1] 0.23%unl_ExpenseExcludingManagementFeePercentageNet [1]    
Net income (loss) (7.65%)unl_PercentageOfConsolidatedNetIncome 8.68%unl_PercentageOfConsolidatedNetIncome    
[1] Annualized