Schedule of Investments (Unaudited) - Treasury Bills (Parenthetical) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2016		Dec. 31, 2015
U.S. Treasury Bills, 0.275% due April 7, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[1],[2]	0.275%
Investment Maturity Date	[1],[2]	Apr. 07, 2016
U.S. Treasury Bills, 0.270% due April 21, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[2]	0.27%
Investment Maturity Date	[2]	Apr. 21, 2016
U.S. Treasury Bills, 0.200% due April 28, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[2]	0.20%
Investment Maturity Date	[2]	Apr. 28, 2016
U.S. Treasury Bills, 0.325% due June 2, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[2]	0.325%
Investment Maturity Date	[2]	Jun. 02, 2016
U.S. Treasury Bills, 0.235% due July 7, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[1],[2]	235.00%
Investment Maturity Date	[1],[2]	Jul. 07, 2016
United States Treasury Obligations [Member]
Schedule Of Investments [Line Items]
United States Treasury Obligations, cost		$ 200,922,264	[2]	$ 133,486,931
U.S. Treasury Bills, 0.205% due January 14, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.205%
Investment Maturity Date	[3]			Jan. 14, 2016
U.S. Treasury Bills, 0.195% due January 21, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.195%
Investment Maturity Date	[3]			Jan. 21, 2016
U.S. Treasury Bills, 0.170% due January 28, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.17%
Investment Maturity Date	[3]			Jan. 28, 2016
U.S. Treasury Bills, 0.200% due February 4, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.20%
Investment Maturity Date	[3]			Feb. 04, 2016
U.S. Treasury Bills, 0.135% due February 11, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.135%
Investment Maturity Date	[3]			Feb. 11, 2016
U.S. Treasury Bills, 0.145% due February 18, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.145%
Investment Maturity Date	[3]			Feb. 18, 2016
U.S. Treasury Bills, 0.140% due February 25, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.14%
Investment Maturity Date	[3]			Feb. 25, 2016
U.S. Treasury Bills, 0.215% due March 3, 2016 [Member]
Schedule Of Investments [Line Items]
Investment Interest Rate	[3]			0.215%
Investment Maturity Date	[3]			Mar. 03, 2016

[1] All or a portion of United States Treasury Obligations are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.

[2] Security may be traded on a discount basis. The interest rate shown represents the discount rate at the most recent auction date of the security prior to period end.

[3] (a)Security may be traded on a discount basis. The interest rate shown represents the discount rate at the most recent auction date of the security prior to year end. (b)A portion of United States Treasury Obligations are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.