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FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) (USD $) | 6 Months Ended |
--- | --- | ---
Jun. 30, 2013 | Jun. 30, 2012 | Nov. 18, 2009
Per Unit Operating Performance: |  |  |  |  |
Net asset value, beginning of period | $ 17.23 |  | $ 21.21 |  | $ 50.00
Total income (loss) | $ 0.07 |  | $ (3.74) |  |
Total expenses | $ (0.09) |  | $ (0.09) |  |
Net decrease in net asset value | $ (0.02) |  | $ (3.83) |  |
Net asset value, end of period | $ 17.21 |  | $ 17.38 |  | $ 50.00
Total Return | (0.12%) |  | (18.06%) |  |
Ratios to Average Net Assets |  |  |  |  |
Total income (loss) | 5.83% |  | (15.50%) |  |
Management fees | 0.75% | [1] | 0.75% | [1] |
Total expenses excluding management fees | 0.38% | [1] | 0.44% | [1] |
Expenses waived | (0.17%) | [1] | (0.20%) | [1] |
Net expenses excluding management fees | 0.21% | [1] | 0.24% | [1] |
Net income (loss) | 5.35% |  | (15.99%) |  |
[1] | Annualized

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