Financial Highlights (Expense Ratios To Average Equity) (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Financial Highlights [Abstract]
Operating expenses, before interest expense and other investment related expenses	[1],[2]	(2.55%)	(3.03%)	(2.59%)	(2.86%)
Ratio Of Incentive Fee To Average Equity	[1],[2]	0.00%	(0.21%)	0.00%	(0.22%)
Interest expense and other investment related expenses	[1],[2]	(2.34%)	(1.98%)	(2.19%)	(2.08%)
Total Expenses	[1],[2]	(4.89%)	(5.22%)	(4.78%)	(5.16%)

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

[2] Ratios are annualized except for the incentive fee which is not annualized.