Statement of Changes in Shareholders' Equity - USD ($)	Total	General Shares [Member]	Shares [Member]
Balance - Value at Dec. 31, 2014	$ 4,036,424,445	$ 736	$ 4,036,423,709
Balance - Shares at Dec. 31, 2014		40	219,400,000
Purchases of Shares - Value	316,102,530		$ 316,102,530
Purchases of Shares - Shares			18,000,000
Redemption of Shares - Value	(1,491,423,279)		$ (1,491,423,279)
Redemption of Shares - Shares			(88,600,000)
Net Increase (Decrease) due to Share Transactions, value	(1,175,320,749)		$ (1,175,320,749)
Net Increase (Decrease) due to Share Transactions, shares			(70,600,000)
Net Income (Loss)
Net Investment Income (Loss)	(25,551,595)	$ (6)	$ (25,551,589)
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	(1,272,153,358)	(294)	(1,272,153,064)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	423,824,269	98	423,824,171
Net Income (Loss)	(873,880,684)	(202)	(873,880,482)
Net Change in Shareholders' Equity, value	(2,049,201,433)	(202)	$ (2,049,201,231)
Net Change in Shareholders' Equity, shares			(70,600,000)
Balance - Value at Dec. 31, 2015	1,987,223,012	$ 534	$ 1,987,222,478
Balance - Shares at Dec. 31, 2015		40	148,800,000
Purchases of Shares - Value	852,904,825		$ 852,904,825
Purchases of Shares - Shares			58,800,000
Redemption of Shares - Value	(648,634,646)		$ (648,634,646)
Redemption of Shares - Shares			(46,000,000)
Net Increase (Decrease) due to Share Transactions, value	204,270,179		$ 204,270,179
Net Increase (Decrease) due to Share Transactions, shares			12,800,000
Net Income (Loss)
Net Investment Income (Loss)	(13,574,300)	$ (3)	$ (13,574,297)
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	(72,710,589)	(20)	(72,710,569)
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	452,256,237	122	452,256,115
Net Income (Loss)	365,971,348	99	365,971,249
Net Change in Shareholders' Equity, value	570,241,527	99	$ 570,241,428
Net Change in Shareholders' Equity, shares			12,800,000
Balance - Value at Dec. 31, 2016	2,557,464,539	$ 633	$ 2,557,463,906
Balance - Shares at Dec. 31, 2016		40	161,600,000
Purchases of Shares - Value	701,045,632		$ 701,045,632
Purchases of Shares - Shares			43,600,000
Redemption of Shares - Value	(1,067,336,515)		$ (1,067,336,515)
Redemption of Shares - Shares			(69,200,000)
Net Increase (Decrease) due to Share Transactions, value	(366,290,883)		$ (366,290,883)
Net Increase (Decrease) due to Share Transactions, shares			(25,600,000)
Net Income (Loss)
Net Investment Income (Loss)	(1,457,317)	$ (1)	$ (1,457,316)
Net Realized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	58,294,421	26	58,294,395
Net Change in Unrealized Gain (Loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	14,348,433	7	14,348,426
Net Income (Loss)	71,185,537	32	71,185,505
Net Change in Shareholders' Equity, value	(295,105,346)	32	$ (295,105,378)
Net Change in Shareholders' Equity, shares			(25,600,000)
Balance - Value at Dec. 31, 2017	$ 2,262,359,193	$ 665	$ 2,262,358,528
Balance - Shares at Dec. 31, 2017		40	136,000,000