Financial Highlights (Expense Ratios To Average Equity) (Details)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Financial Highlights [Abstract]
Operating expenses, before interest expense and other investment related expenses	(2.63%)	[1],[2]	(2.81%)	[1],[2]
Interest expense and other investment related expenses	(2.14%)	[1],[2]	(1.97%)	[1],[2]
Total Expenses	(4.77%)	[1],[2]	(4.78%)	[1],[2]

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

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