Financial Highlights (Expense Ratios To Average Equity) (Details)		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Financial Highlights [Abstract]
Operating expenses, before interest expense and other investment related expenses	[1],[2]	(2.82%)	(2.63%)
Interest expense and other investment related expenses	[1],[2]	(2.90%)	(2.14%)
Total Expenses	[1],[2]	(5.72%)	(4.77%)

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

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