Financial Highlights (Expense Ratios To Average Equity) (Details)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Financial Highlights [Abstract]
Operating expenses before incentive fee, interest expense, and other investment related expenses	(2.80%)	[1]	(2.74%)	[1]	(2.94%)	[1]
Ratio Of Incentive Fee To Average Equity	(0.21%)	[1]	(1.42%)	[1]	(4.43%)	[1]
Interest expense and other investment related expenses	(2.14%)	[1]	(1.95%)	[1]	(1.80%)	[1]
Total Expenses	(5.15%)	[1]	(6.11%)	[1]	(9.17%)	[1]

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