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FINANCIAL HIGHLIGHTS (Per share Performance Data and Other Supplemental Financial Data) (Detail) - $ / shares | 6 Months Ended
--- | ---
Jun. 30, 2016 | Jun. 30, 2015
Per Share Operating Performance: |  |  |
Net asset value, beginning of period |  | $ 11.02 | $ 20.15
Total income (loss) |  | 0.58 | (0.15)
Total expenses |  | (0.04) | (0.07)
Net increase (decrease) in net asset value |  | 0.54 | (0.22)
Net asset value, end of period |  | $ 11.56 | $ 19.93
Total Return |  | 4.90% | (1.09%)
Ratios to Average Net Assets |  |  |
Total income (loss) |  | 13.58% | 9.69%
Management fees | [1] | 0.45% | 0.45%
Expenses excluding management fees | [1] | 0.33% | 0.26%
Net income (loss) |  | 13.19% | 9.34%
[1] | Annualized.

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