Statement of Changes in Shareholders' Equity - USD ($)	Total	General Shares [Member]	Shares [Member]
Balance - Value at Dec. 31, 2013	$ 1,218,756,970	$ 971	$ 1,218,755,999
Balance - Shares at Dec. 31, 2013		40	50,200,000
Purchases of Shares - Value	350,188,749		$ 350,188,749
Purchases of Shares - Shares			12,600,000
Redemption of Shares - Value	(559,838,929)		$ (559,838,929)
Redemption of Shares - Shares			(21,000,000)
Net Increase (Decrease) due to Share Transactions, value	(209,650,180)		$ (209,650,180)
Net Increase (Decrease) due to Share Transactions, shares			(8,400,000)
Net Income (Loss)
Net Investment Income (Loss)	(11,669,867)	$ (9)	$ (11,669,858)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	55,655,433	43	55,655,390
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(15,144,647)	(12)	(15,144,635)
Net Income (Loss)	28,840,919	22	28,840,897
Net Change in Shareholders' Equity, value	(180,809,261)	22	$ (180,809,283)
Net Change in Shareholders' Equity, shares			(8,400,000)
Balance - Value at Dec. 31, 2014	1,037,947,709	$ 993	$ 1,037,946,716
Balance - Shares at Dec. 31, 2014		40	41,800,000
Purchases of Shares - Value	139,873,537		$ 139,873,537
Purchases of Shares - Shares			6,200,000
Redemption of Shares - Value	(335,872,630)		$ (335,872,630)
Redemption of Shares - Shares			(15,400,000)
Net Increase (Decrease) due to Share Transactions, value	(195,999,093)		$ (195,999,093)
Net Increase (Decrease) due to Share Transactions, shares			(9,200,000)
Net Income (Loss)
Net Investment Income (Loss)	(7,780,737)	$ (8)	$ (7,780,729)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(215,438,584)	(213)	(215,438,371)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	55,149,332	55	55,149,277
Net Income (Loss)	(168,069,989)	(166)	(168,069,823)
Net Change in Shareholders' Equity, value	(364,069,082)	(166)	$ (364,068,916)
Net Change in Shareholders' Equity, shares			(9,200,000)
Balance - Value at Dec. 31, 2015	673,878,627	$ 827	$ 673,877,800
Balance - Shares at Dec. 31, 2015		40	32,600,000
Purchases of Shares - Value	315,204,237		$ 315,204,237
Purchases of Shares - Shares			15,000,000
Redemption of Shares - Value	(234,961,105)		$ (234,961,105)
Redemption of Shares - Shares			(11,400,000)
Net Increase (Decrease) due to Share Transactions, value	80,243,132		$ 80,243,132
Net Increase (Decrease) due to Share Transactions, shares			3,600,000
Net Income (Loss)
Net Investment Income (Loss)	(4,792,983)	$ (4)	$ (4,792,979)
Net Realized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(2,819,080)	(3)	(2,819,077)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations and Commodity Futures Contracts	(23,280,126)	(21)	(23,280,105)
Net Income (Loss)	(30,892,189)	(28)	(30,892,161)
Net Change in Shareholders' Equity, value	49,350,943	(28)	$ 49,350,971
Net Change in Shareholders' Equity, shares			3,600,000
Balance - Value at Dec. 31, 2016	$ 723,229,570	$ 799	$ 723,228,771
Balance - Shares at Dec. 31, 2016		40	36,200,000