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FINANCIAL INSTRUMENTS, OFF-BALANCE SHEET RISKS AND CONTINGENCIES (Details Textual) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Money Market Funds, at Carrying Value $ 10,000,000us-gaap_MoneyMarketFundsAtCarryingValue $ 8,010,771us-gaap_MoneyMarketFundsAtCarryingValue
Cash Deposits and Investments In Treasuries $ 106,090,732bno_CashDepositsAndInvestmentsInTreasuries $ 45,561,253bno_CashDepositsAndInvestmentsInTreasuries