Schedule of Investments (Unaudited) - Futures Contracts		9 Months Ended	12 Months Ended
		Sep. 30, 2018 USD ($) Contract	Dec. 31, 2017 USD ($) Contract
Schedule Of Investments [Line Items]
Total Investments in Securities		$ 30,222,867	$ 40,028,791
Short [Member] | Futures [Member] | United States of America, Dollars [Member] | ICE FUTURES U.S. [Member]
Schedule Of Investments [Line Items]
Number of Contracts | Contract		320	424
Expiration Date		Dec. 31, 2018	Mar. 31, 2018
Notional Value		$ (30,315,840)	$ (38,934,224)
Total Investments in Securities	[1]	(104,932)	583,889
Unrealized Appreciation (Depreciation)	[1]	$ (104,932)	$ 583,889

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