Condensed Schedule of Investments (Parenthetical) - USD ($)		9 Months Ended	12 Months Ended
		Sep. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, amortized cost		$ 8,993,980	$ 16,996,479
U.S. Treasury bills, 0.19% [Member] | U.S. Treasury Bills [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, amortized cost			$ 10,998,375
Investment, Interest rate	[1]		0.19%
U.S. Treasury bills, 0.125% [Member] | U.S. Treasury Bills [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, amortized cost			$ 5,998,104
Investment, Interest rate	[1]		0.125%
U.S. Treasury bills, 0.28% [Member] | U.S. Treasury Bills [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, amortized cost		$ 8,993,980
Investment, Interest rate	[1]	0.28%

[1] Liquid non-cash held as collateral.