Financial Highlights (Net Investment Income Ratio To Average Equity) (Details)		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Investment Company, Financial Highlights [Abstract]
Net Investment Income (Loss) Ratio	[1],[2]	6.75%	7.36%

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

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