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Financial Highlights (Tables) | 9 Months Ended
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Sep. 30, 2012
Financial Highlights [Abstract] |
Per Unit Performance Data and Other Supplemental Financial Data | The following table presents per unit performance data and other supplemental financial data for the nine months ended September 30, 2012 and 2011 for the unitholders. This information has been derived from information presented in the condensed financial statements.
|  | For the nine months ended September 30, 2012 (Unaudited) |  |  | For the nine months ended September 30, 2011 (Unaudited) |
Per Unit Operating Performance: |  |  |  |  |  |  |  |
Net asset value, beginning of period |  | $ | 21.21 |  |  | $ | 35.02 |
Total income (loss) |  |  | (2.40 | ) |  |  | (6.85 | )
Total expenses |  |  | (0.13 | ) |  |  | (0.23 | )
Net decrease in net asset value |  |  | (2.53 | ) |  |  | (7.08 | )
Net asset value, end of period |  | $ | 18.68 |  |  | $ | 27.94 |
Total Return |  |  | (11.93 | )% |  |  | (20.22 | )%
Ratios to Average Net Assets |  |  |  |  |  |  |  |
Total income (loss) |  |  | (2.93 | )% |  |  | (21.56 | )%
Management fees* |  |  | 0.75 | % |  |  | 0.75 | %
Total expenses excluding management fees* |  |  | 0.39 | % |  |  | 0.65 | %
Expenses waived* |  |  | (0.16 | )% |  |  | (0.44 | )%
Net expenses excluding management fees* |  |  | 0.23 | % |  |  | 0.21 | %
Net income (loss) |  |  | (3.66 | )% |  |  | (22.28 | )%
* | Annualized

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