Statements of Changes in Net Assets (Unaudited) - USD ($)		9 Months Ended		12 Months Ended
		Sep. 30, 2015		Dec. 31, 2014
Net Assets, Beginning of Period	[1]	$ 787,119,766	[2]	$ 1,171,092,949
Operations:
Net investment loss		(4,820,193)		(8,000,322)	[1]
Net realized loss		(222,027,931)		(377,331,622)	[1]
Net change in unrealized appreciation/depreciation		52,537,444		5,956,373	[1]
Net decrease in net assets resulting from operations		(174,310,680)		(379,375,571)	[1]
Capital Share Transactions:
Contributions for Shares issued		191,263,396		347,622,705	[1]
Distributions for Shares redeemed		(56,371,281)		(352,220,317)	[1]
Net increase (decrease) in net assets from capital share transactions		134,892,115		(4,597,612)	[1]
Decrease in net assets		(39,418,565)		(383,973,183)	[1]
Net Assets, End of Period		$ 747,701,201		$ 787,119,766	[1],[2]
Shares issued and redeemed
Shares issued (in Shares)		9,850,000		11,500,000	[1]
Shares redeemed (in Shares)		(2,800,000)		(11,050,000)	[1]
Net increase in Shares issued and outstanding (in Shares)		7,050,000		450,000	[1]

[1] Previously reported as "Statements of Changes in Shareholders' Capital." Please refer to Note 2A.

[2] Previously reported as "Statements of Financial Condition." Please refer to Note 2A.