v3.10.0.1

Financial Highlights (Net Asset Value Based Total Return For A Shareholder) (Details) | 3 Months Ended | 6 Months Ended
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Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Investment Company, Financial Highlights [Abstract] |  |  |  |  |
Total Return | [1] | 3.78% | 0.82% | 8.24% | 3.32%
[1] | Total return is calculated assuming reinvestment of distributions at shareholders' equity per share during the period.

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- References No definition available. + Details
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- Definition Percentage increase (decrease), after deduction of incentive fee, in fund net asset value. Includes, but is not limited to, interest and dividend income (loss) and realized and unrealized gain (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 205 -Section 50 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=25866437&loc=d3e10421-115837 + Details
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