Financial Highlights (Expense Ratios To Average Shareholders Equity) (Details)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Financial Highlights [Abstract]
Operating expenses before incentive fee and interest expense	(2.97%)	[1],[2]	(3.06%)	[1],[2]	(3.04%)	[1],[2]	(3.10%)	[1],[2]
Incentive fee	(0.58%)	[1],[2]	0.00%	[1],[2]	(0.59%)	[1],[2]	(0.15%)	[1],[2]
Interest expense	(2.02%)	[1],[2]	(1.65%)	[1],[2]	(1.98%)	[1],[2]	(1.61%)	[1],[2]
Total Expenses	(5.57%)	[1],[2]	(4.71%)	[1],[2]	(5.61%)	[1],[2]	(4.86%)	[1],[2]

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

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