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FINANCIAL HIGHLIGHTS (Tables) | 9 Months Ended
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Sep. 30, 2013
Supplemental Financial Information Disclosure [Abstract] |
Schedule Of Per Unit Performance Data and Other Financial Data | The following table presents per unit performance data and other supplemental financial data for the nine months ended September 30, 2013 and 2012 for the unitholders. This information has been derived from information presented in the condensed financial statements.
|  | For the nine months ended September 30, 2013 (Unaudited) |  |  | For the nine months ended September 30, 2012 (Unaudited) |  |
Per Unit Operating Performance: |  |  |  |  |  |  |  |  |
Net asset value, beginning of period |  | $ | 40.98 | * |  | $ | 37.27 | * |
Total income |  |  | 1.71 |  |  |  | 3.62 | * |
Total expenses |  |  | (0.30) |  |  |  | (0.29) | * |
Net increase in net asset value |  |  | 1.41 |  |  |  | 3.33 | * |
Net asset value, end of period |  | $ | 42.39 |  |  | $ | 40.60 | * |
Total Return |  |  | 3.44 | % |  |  | 8.93 | % |
Ratios to Average Net Assets |  |  |  |  |  |  |  |  |
Total income |  |  | 3.36 | % |  |  | 8.40 | % |
Management fees** |  |  | 0.75 | % |  |  | 0.75 | % |
Total expenses excluding management fees** |  |  | 0.40 | % |  |  | 0.30 | % |
Expenses waived** |  |  | (0.16) | % |  |  | (0.07) | % |
Net expenses excluding management fees** |  |  | 0.24 | % |  |  | 0.23 | % |
Net income |  |  | 2.62 | % |  |  | 7.66 | % |
* | On August 26, 2013, USBO executed a 2-for-1 forward unit split for all unitholders of record as of the close of markets on August 26, 2013. The 2-for-1 forward unit split was payable after the close of markets on August 28, 2013. USBO began trading at its post split price on August 29, 2013. The Financial Highlights (Unaudited) have been adjusted for the periods shown to reflect the 2-for-1 forward unit split on a retroactive basis.
** | Annualized.

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