Financial Highlights (Expense Ratios to Average Equity) (Details) |
12 Months Ended |
|---|---|
Dec. 31, 2018 | |
| Investment Company, Financial Highlights [Abstract] | |
| Ratio Of Operating Expenses Before Incentive Fee, Interest Expense, and Other Investment Related Expenses To Average Equity | (2.86%) |
| Investment Company, Incentive Fee to Average Net Assets | (0.12%) |
| Ratio Of Interest and other investment related Expenses To Average Equity | (12.03%) |
| Investment Company, Expense Ratio after Incentive Allocation | (15.01%) |