FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) - $ / shares		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014
Per Share Operating Performance:
Net asset value, beginning of period		$ 13.69	$ 18.32
Total income (loss)		(2.32)	(0.14)
Net expenses		(0.09)	(0.14)
Net decrease in net asset value		(2.41)	(0.28)
Net asset value, end of period		$ 11.28	$ 18.04
Total Return		(17.60%)	(1.53%)
Ratios to Average Net Assets
Total income (loss)		(14.87%)	4.47%
Management fees	[1]	0.75%	0.75%
Total expenses excluding management fees	[1]	0.66%	0.99%
Expenses waived	[1]	(0.51%)	(0.80%)
Net expenses excluding management fees	[1]	0.15%	0.19%
Net income (loss)		(15.55%)	3.76%

[1] Annualized