Financial Highlights (Net Asset Value Based Total Return For A Shareholder) (Details)	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Financial Highlights [Abstract]
Total Return	1.32%	[1]	1.82%	[1]	8.44%	[1]	11.57%	[1]

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