Financial Highlights (Net Asset Value Based Total Return For A Shareholder) (Details)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Financial Highlights [Abstract]
Total Return	8.77%	[1]	14.19%	[1]	22.16%	[1]

[1] Total return is calculated assuming reinvestment of distributions at shareholders' equity per share during the period.