Statement of Changes in Shareholders' Equity (Unaudited) - USD ($)	Total	General Shares [Member]	Shares [Member]
Balance - Value at Dec. 31, 2014	$ 220,647,504	$ 640	$ 220,646,864
Balance - Shares at Dec. 31, 2014		40	13,800,000
Sale of Shares - Value	44,894,499		$ 44,894,499
Sale of Shares - Shares			3,000,000
Redemption of Shares - Value	(52,121,494)		$ (52,121,494)
Redemption of Shares - Shares			(3,400,000)
Net Increase (Decrease) due to Share Transactions, value	(7,226,995)		$ (7,226,995)
Net Increase (Decrease) due to Share Transactions, shares			(400,000)
Net Income (Loss)
Net Investment Income (Loss)	(353,749)	$ (1)	$ (353,748)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(14,326,345)	(47)	(14,326,298)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	4,975,336	16	4,975,320
Net Income (Loss)	(9,704,758)	(32)	(9,704,726)
Net Change in Shareholders' Equity, value	(16,931,753)	(32)	$ (16,931,721)
Net Change in Shareholders' Equity, shares			(400,000)
Balance - Value at Mar. 31, 2015	203,715,751	$ 608	$ 203,715,143
Balance - Shares at Mar. 31, 2015		40	13,400,000
Balance - Value at Dec. 31, 2015	113,983,312	$ 475	$ 113,982,837
Balance - Shares at Dec. 31, 2015		40	9,600,000
Sale of Shares - Value	2,561,538		$ 2,561,538
Sale of Shares - Shares			200,000
Redemption of Shares - Value	(18,339,980)		$ (18,339,980)
Redemption of Shares - Shares			(1,600,000)
Net Increase (Decrease) due to Share Transactions, value	(15,778,442)		$ (15,778,442)
Net Increase (Decrease) due to Share Transactions, shares			(1,400,000)
Net Income (Loss)
Net Investment Income (Loss)	(207,669)	$ (1)	$ (207,668)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(15,634,617)	(92)	(15,634,525)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	19,395,662	114	19,395,548
Net Income (Loss)	3,553,376	21	3,553,355
Net Change in Shareholders' Equity, value	(12,225,066)	21	$ (12,225,087)
Net Change in Shareholders' Equity, shares			(1,400,000)
Balance - Value at Mar. 31, 2016	$ 101,758,246	$ 496	$ 101,757,750
Balance - Shares at Mar. 31, 2016		40	8,200,000