Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net Income (Loss)	$ (620,141)	$ (10,249,593)
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Cost of securities purchased	(506,491,544)	(317,560,413)
Proceeds from securities sold and matured	393,979,217	393,974,695
Cost of affiliated investments purchased	(193,623,649)	(430,944,975)
Proceeds from affiliated investments sold	217,719,212	351,091,971
Net accretion of discount on United States Treasury Obligations	(2,077,793)	(851,088)
Net realized (gain) loss on United States Treasury Obligations and Affiliated Investments	745	4,764
Net change in unrealized (gain) loss on United States Treasury Obligations and Affiliated Investments	(196,752)	7,641
Change in operating assets and liabilities:
Variation margin - Commodity Futures Contracts	(3,475,596)	(1,697,457)
Dividends from affiliates	(5,090)	(1,309)
Management fees	95,022	28,960
Brokerage commissions and fees	(10,672)	1,890
Net cash provided by (used for) operating activities	(94,707,041)	(16,194,914)
Cash flows from financing activities:
Proceeds from purchases of Shares	115,107,662	119,100,783
Redemption of Shares	(22,661,544)	(105,087,105)
Net cash provided by (used for) financing activities	92,446,118	14,013,678
Net change in cash	(2,260,923)	(2,181,236)
Cash at beginning of period	2,260,923	2,181,236
Cash at end of period	0	0
Supplemental disclosure of cash flow information
Cash paid for interest	$ 3,838	$ 2,184