Financial Highlights (Expense Ratios To Average Equity) (Details) |
3 Months Ended | 9 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
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| Investment Company, Financial Highlights [Abstract] | |||||||||
| Operating expenses, before interest expense and other investment related expenses | [1],[2] | (2.76%) | (2.89%) | (2.80%) | (2.88%) | ||||
| Interest expense and other investment related expenses | [1],[2] | (6.32%) | (3.69%) | (5.69%) | (3.43%) | ||||
| Total Expenses | [1],[2] | (9.08%) | (6.58%) | (8.49%) | (6.31%) | ||||
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