Schedule of Investments (Unaudited) - Futures Contracts		9 Months Ended		12 Months Ended
		Sep. 30, 2017 USD ($) Contract		Dec. 31, 2016 USD ($) Contract
Schedule of Investments [Line Items]
Value		$ 643,570,293		$ 849,945,124
Futures [Member]
Schedule of Investments [Line Items]
Value	[1]	6,255,165
Unrealized Appreciation (Depreciation)		$ 6,255,165	[1]	$ 1,988,810	[2]
Futures [Member] | United States of America, Dollars [Member] | ICE FUTURES U.S. [Member] | Long [Member]
Schedule of Investments [Line Items]
Number of Contracts | Contract		7,026		8,270
Expiration Date		Dec. 31, 2017		Mar. 31, 2017
Notional Value		$ 652,595,958		$ 845,905,220
Value	[1]	6,255,165
Unrealized Appreciation (Depreciation)		$ 6,255,165	[1]	$ 1,988,810	[2]

[1] Unrealized Appreciation (Depreciation) and Value are presented above, net by contract.

[2] Unrealized Appreciation (Depreciation) is presented above, net by contract.