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Summary Of Significant Accounting Policies (Details Textual)	Feb. 29, 2012
Number Rof Shares Per Baskets	50,000
Redemption Baskets [Member] | Prior to July 1, 2011 [Member]
Number Rof Shares Per Baskets	100,000

X

- Definition

Number rof shares Per Baskets.

+ References

No definition available.

+ Details

Name:	bno_NumberRofSharesPerBaskets
Namespace Prefix:	bno_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant