Financial Highlights (Net Investment Income Ratio To Average Equity) (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Investment Company, Financial Highlights [Abstract]
Net Investment Income (Loss) Ratio	[1],[2]	4.95%	3.80%	5.86%	5.14%

[1] Average equity is calculated using month end values.

[2] Includes all items of income and expense on an annualized basis.