Schedule of Investments (Unaudited) - Treasury Bills (Parenthetical) - USD ($)		6 Months Ended		12 Months Ended
		Jun. 30, 2016		Dec. 31, 2015
U.S. Treasury Bills, 0.190% due July 7, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1]	0.19%
Investment Maturity Date	[1]	Jul. 07, 2016
U.S. Treasury Bills, 0.250% due July 21, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1]	0.25%
Investment Maturity Date	[1]	Jul. 21, 2016
U.S. Treasury Bills, 0.260% due July 28, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1]	0.26%
Investment Maturity Date	[1]	Jul. 28, 2016
U.S. Treasury Bills, 0.275% due August 4, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1]	0.275%
Investment Maturity Date	[1]	Aug. 04, 2016
U.S. Treasury Bills, 0.340% due September 1, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1]	0.34%
Investment Maturity Date	[1]	Sep. 01, 2016
U.S. Treasury Bills, 0.270% due October 6, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1],[2]	0.27%
Investment Maturity Date	[1],[2]	Oct. 06, 2016
Restricted for maintenance margin	[1]	$ 264,814,500
U.S. Treasury Bills, 0.400% due October 27, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[1]	0.40%
Investment Maturity Date	[1]	Oct. 27, 2016
United States Treasury Obligations [Member]
Schedule of Investments [Line Items]
United States Treasury Obligations, cost		$ 2,383,864,387	[1]	$ 1,936,918,775	[3],[4]
U.S. Treasury Bills, 0.235% due January 7, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.235%
Investment Maturity Date	[3],[4]			Jan. 07, 2016
U.S. Treasury Bills, 0.205% due January 14, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.205%
Investment Maturity Date	[3],[4]			Jan. 14, 2016
U.S. Treasury Bills, 0.195% due January 21, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.195%
Investment Maturity Date	[3],[4]			Jan. 21, 2016
Restricted for maintenance margin	[3],[4]			$ 399,960,000
U.S. Treasury Bills, 0.170% due January 28, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.17%
Investment Maturity Date	[3],[4]			Jan. 28, 2016
U.S. Treasury Bills, 0.200% due February 4, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.20%
Investment Maturity Date	[3],[4]			Feb. 04, 2016
U.S. Treasury Bills, 0.135% due February 11, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.135%
Investment Maturity Date	[3],[4]			Feb. 11, 2016
U.S. Treasury Bills, 0.140% due February 25, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.14%
Investment Maturity Date	[3],[4]			Feb. 25, 2016
U.S. Treasury Bills, 0.280% due March 10, 2016 [Member]
Schedule of Investments [Line Items]
Investment Interest Rate	[3],[4]			0.28%
Investment Maturity Date	[3],[4]			Mar. 10, 2016

[1] 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.

[2] United States Treasury Obligations of $264,814,500 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.

[3] 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.

[4] United States Treasury Obligations of $399,960,000 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.