Condensed Statements of Operations (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Gain (loss) on trading of commodity futures contracts:
Realized gain (loss) on closed positions	$ 1,725,380us-gaap_GainLossOnSaleOfInvestments	$ (98,080)us-gaap_GainLossOnSaleOfInvestments
Change in unrealized gain (loss) on open positions	(4,188,770)us-gaap_UnrealizedGainLossOnInvestments	(276,270)us-gaap_UnrealizedGainLossOnInvestments
Dividend income	522us-gaap_DividendIncomeOperating	37us-gaap_DividendIncomeOperating
Interest income	8,117us-gaap_InterestIncomeOperating	1,751us-gaap_InterestIncomeOperating
ETF transaction fees	10,500us-gaap_OtherIncome	3,150us-gaap_OtherIncome
Total income (loss)	(2,444,251)bno_TotalIncomeLoss	(369,412)bno_TotalIncomeLoss
Expenses
General Partner management fees (Note 3)	153,435us-gaap_AssetManagementCosts	49,695us-gaap_AssetManagementCosts
Professional fees	31,278us-gaap_ProfessionalFees	40,680us-gaap_ProfessionalFees
Brokerage commissions	25,577	4,109
Directors' fees and insurance	2,547us-gaap_NoninterestExpenseDirectorsFees	1,935us-gaap_NoninterestExpenseDirectorsFees
Total expenses	212,837bno_TotalExpenses	96,419bno_TotalExpenses
Expense waiver (Note 3)	(27,677)bno_ExpenseWaiver	(30,741)bno_ExpenseWaiver
Net expenses	185,160bno_TotalExpensesNetOfExpenseWaiver	65,678bno_TotalExpensesNetOfExpenseWaiver
Net income (loss)	$ (2,629,411)us-gaap_NetIncomeLoss	$ (435,090)us-gaap_NetIncomeLoss
Net income (loss) per limited partnership share	$ (1.91)	$ 0.75
Net income (loss) per weighted average limited partnership share	$ (0.67)	$ (0.69)
Weighted average limited partnership shares outstanding	3,921,111	626,667

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