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FINANCIAL HIGHLIGHTS (Tables) | 12 Months Ended
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Dec. 31, 2015
Financial Highlights [Abstract] |
Per Unit Performance Data and Other Supplemental Financial Data | This information has been derived from information presented in the financial statements.
|  | Year Ended |  |  | Year Ended |  |  | Year Ended |
|  | December 31, 2015 |  |  | December 31, 2014 |  |  | December 31, 2013 |
Per Share Operating Performance: |  |  |  |  |  |  |  |  |  |  |  |
Net asset value, beginning of year |  | $ | 13.69 |  |  | $ | 18.32 |  |  | $ | 17.23 |
Total income (loss) |  |  | (3.86) |  |  |  | (4.33) |  |  |  | 1.32 |
Net expenses |  |  | (0.11) |  |  |  | (0.30) |  |  |  | (0.23) |
Net increase (decrease) in net asset value |  |  | (3.97) |  |  |  | (4.63) |  |  |  | 1.09 |
Net asset value, end of year |  | $ | 9.72 |  |  | $ | 13.69 |  |  | $ | 18.32 |
Total Return |  |  | (29.00) | % |  |  | (25.27) | % |  |  | 6.33 | %
Ratios to Average Net Assets |  |  |  |  |  |  |  |  |  |  |  |
Total income (loss) |  |  | (27.80) | % |  |  | (19.76) | % |  |  | 13.23 | %
Management fees |  |  | 0.75 | % |  |  | 0.75 | % |  |  | 0.75 | %
Total expenses excluding management fees |  |  | 0.71 | % |  |  | 0.85 | % |  |  | 0.51 | %
Expenses waived |  |  | (0.56) | % |  |  | (0.67) | % |  |  | (0.30) | %
Net expenses excluding management fees |  |  | 0.15 | % |  |  | 0.18 | % |  |  | 0.21 | %
Net income (loss) |  |  | (28.70) | % |  |  | (20.70) | % |  |  | 12.27 | %

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