Condensed Statements of Cash Flows (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash Flows from Operating Activities:
Net income (loss)	$ (2,629,411)us-gaap_NetIncomeLoss	$ (435,090)us-gaap_NetIncomeLoss
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
(Increase) decrease in commodity futures trading account - cash and cash equivalents	(8,826,163)	(2,897,576)
Unrealized (gain) loss on futures contracts	4,188,770	276,270
(Increase) decrease in receivable from General Partner	66,639	49,912
(Increase) decrease in dividends receivable	(314)	421
(Increase) decrease in directors' fees and insurance receivable	(1,502)	(2,671)
(Increase) decrease in ETF transaction fees receivable	700	0
Increase (decrease) in General Partner management fees payable	42,941	(1,081)
Increase (decrease) in professional fees payable	(48,113)	(99,762)
Increase (decrease) in brokerage commissions payable	2,860	(110)
Increase (decrease) in directors' fees and insurance payable	(338)	(209)
Net cash provided by (used in) operating activities	(7,203,931)	(3,109,896)
Cash Flows from Financing Activities:
Addition of partnership shares	70,948,692	10,745,769
Redemption of partnership shares	(2,041,445)bno_PaymentsToPartnershipRedemption	(10,799,701)bno_PaymentsToPartnershipRedemption
Net cash provided by (used in) financing activities	68,907,247	(53,932)
Net Increase (Decrease) in Cash and Cash Equivalents	61,703,316	(3,163,828)
Cash and Cash Equivalents, beginning of period	36,408,502	25,257,312
Cash and Cash Equivalents, end of period	$ 98,111,818	$ 22,093,484

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