Financial Highlights (Net Investment Income Ratio To Average Shareholders Equity) (Details)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Financial Highlights [Abstract]
Net Investment Income (2)	5.59%	[1],[2]	11.58%	[1],[2]	7.66%	[1],[2]

[1] Includes incentive fee in calculation which can vary substantially over periods.

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