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FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) - $ / shares | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Per Share Operating Performance: |  |  |  |  |  |  |
Net asset value, beginning of year | [2],[3] | $ 37.18 | [1] | $ 34.76 |  | $ 58.50 |
Total income (loss) |  | (13.49) |  | 2.77 | [2] | (23.12) | [2]
Total expenses |  | (0.35) |  | (0.35) |  | (0.62) | [2]
Net increase (decrease) in net asset value |  | (13.84) |  | 2.42 | [2] | (23.74) | [2]
Net asset value, end of year | [2],[3] | $ 23.34 | [1] | $ 37.18 | [1] | $ 34.76 |
Total Return |  | (37.22%) |  | 6.90% |  | (40.60%) |
Ratios to Average Net Assets |  |  |  |  |  |  |
Total income (loss) |  | (37.75%) |  | 19.27% |  | (39.08%) |
Management fees |  | 0.60% |  | 0.60% |  | 0.60% |
Expenses excluding management fees |  | 0.70% |  | 0.52% |  | 0.67% |
Net income (loss) |  | (39.05%) |  | 18.15% |  | (40.35%) |
[1] | On January 4, 2018, there was a 1-for-4 reverse share split. Historical shares outstanding, net asset value per share and market value per share have been adjusted to reflect the 1-for-4 reverse share split on a retroactive basis.
[2] | On January 4, 2018, there was a 1-for-4 reverse share split. The Financial Highlights have been adjusted for the period shown to reflect the 1-for-4 reverse share split on a retroactive basis.
[3] | On January 4, 2018, there was a 1-for-4 reverse share split. The Statement of Changes in Partners’ Capital have been adjusted for the period shown to reflect the 1-for-4 reverse share split on a retroactive basis.

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