Financial Highlights (Net Asset Based Total Return For A Shareholder) (Details)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Financial Highlights [Abstract]
Total Return	3.36%	[1]	1.57%	[1]	7.03%	[1]	9.57%	[1]

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