Financial Highlights (Net Investment Income Ratio To Average Equity) (Details)		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Financial Highlights [Abstract]
Net Investment Income	[1],[2]	5.24%	4.98%	6.31%	5.79%

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

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