Statements of Cash Flows - USD ($)		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Cash flows from operating activities:
Net Income (Loss)		$ 71,185,537		$ 365,971,348		$ (873,880,684)
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Cost of securities purchased		(6,226,946,742)		(8,367,614,637)		(10,667,467,852)
Proceeds from securities sold and matured		6,805,695,866		7,906,957,513		12,810,168,648
Cost of affiliated investments purchased		(4,198,801,266)		(1,362,944,962)
Proceeds from affiliated investments sold		4,011,837,165		1,231,915,157
Net accretion of discount on United States Treasury Obligations		(14,035,908)		(6,308,729)		(715,663)
Net realized (gain) loss on United States Treasury Obligations and Affiliated Investments		44,293		(19,938)		(14,586)
Net change in unrealized (gain) loss on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts		(10,588,043)		(50,991,385)		(423,824,269)
Change in operating assets and liabilities:
Cash transfer to Commodity Broker to satisfy variation margin requirements (Note 4)						(584,258,422)
Cash received (paid) to Commodity Broker to satisfy open variation margin, net (Note 4)						267,424,485
Dividends from affiliates		(51,445)		(42,071)
Variation margin - Commodity Futures Contracts		(10,540,724)		16,211,441		(16,665,912)
LME Commodity Futures Contracts		(506,436)		(24,721,084)		12,568,839
Management fee		(189,346)		239,375		(1,508,466)
Brokerage commissions and fees		(2,235)		14		425
Net cash provided by (used for) operating activities		427,100,716		(291,347,958)		521,826,543
Cash flows from financing activities:
Proceeds from purchases of Shares		641,160,206		852,904,825		316,102,530
Redemption of Shares		(1,067,336,515)		(648,634,646)		(1,491,423,279)
Net cash provided by (used for) financing activities		(426,176,309)		204,270,179		(1,175,320,749)
Net change in cash		924,407		(87,077,779)		(653,494,206)
Cash at beginning of period		5,015,157	[1]	92,092,936	[1]	745,587,142	[2]
Cash at end of period	[1]	5,939,564		5,015,157		92,092,936
Supplemental disclosure of cash flow information
Cash paid for interest		$ 68,451		$ 141,261		$ 277,439

[1] Cash at December 31, 2017, 2016 and 2015 reflects cash held by the Custodian.

[2] Cash at December 31, 2014 reflects cash held by the Predecessor Commodity Broker.