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FINANCIAL HIGHLIGHTS (Details) (USD $)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Jun. 02, 2010
Per Share Operating Performance:      
Net asset value, beginning of period $ 22.39bno_NetAssetValuePerUnit $ 43.81bno_NetAssetValuePerUnit $ 50.00bno_NetAssetValuePerUnit
Total income (loss) $ (1.86)bno_TotalIncomePerUnit $ (0.65)bno_TotalIncomePerUnit  
Net expenses $ (0.05)bno_TotalExpensePerUnit $ (0.10)bno_TotalExpensePerUnit  
Net increase (decrease) in net asset value $ (1.91)bno_NetIncreaseDecreaseInNetAssetValue $ (0.75)bno_NetIncreaseDecreaseInNetAssetValue  
Net asset value, end of period $ 20.48bno_NetAssetValuePerUnit $ 43.06bno_NetAssetValuePerUnit $ 50.00bno_NetAssetValuePerUnit
Total Return (8.53%)bno_PercentageOfTotalReturn (1.71%)bno_PercentageOfTotalReturn  
Ratios to Average Net Assets      
Total income (loss) (2.95%)bno_PercentageOfTotalIncomeOnNetAssets (1.37%)bno_PercentageOfTotalIncomeOnNetAssets  
Management fees 0.75%bno_PercentageOfManagementFeesOnNetAssets [1] 0.75%bno_PercentageOfManagementFeesOnNetAssets [1]  
Total expenses excluding management fees 0.29%bno_PercentageOfTotalExpensesExcludingManagementFeesOnNetAssets [1] 0.70%bno_PercentageOfTotalExpensesExcludingManagementFeesOnNetAssets [1]  
Expenses waived (0.13%)bno_PercentageOfExpensesWaivedOnNetAssets [1] (0.46%)bno_PercentageOfExpensesWaivedOnNetAssets [1]  
Net expenses excluding management fees 0.16%bno_PercentageOfNetExpensesExcludingManagementFeeOnNetAssets [1] 0.24%bno_PercentageOfNetExpensesExcludingManagementFeeOnNetAssets [1]  
Net income (loss) (3.17%)bno_PercentageOfNetIncomeOnNetAssets (1.62%)bno_PercentageOfNetIncomeOnNetAssets  
[1] Annualized