Schedule of Investments (Unaudited) - Treasury Bills and Money Market Fund - USD ($)		6 Months Ended		12 Months Ended
		Jun. 30, 2017		Dec. 31, 2016
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		96.22%		99.12%
Value		$ 1,371,935,248		$ 2,403,838,023
Affiliated investments, at value		346,560,479		131,029,805
Total Investments		1,718,495,727		2,534,867,828
Investments, cost		$ 1,717,876,964		2,534,934,371
Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		19.41%
Affiliated investments, at value		$ 346,560,479
Affiliated Investments, at Cost		$ 346,025,265		$ 131,029,805
U.S. Treasury Bills, 0.840% due July 6, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	14.33%
Value	[1]	$ 255,983,872
Principal Value	[1]	$ 256,000,000
Investment Interest Rate		0.84%
Investment Maturity Date		Jul. 06, 2017
U.S. Treasury Bills, 0.890% due July 27, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1],[2]	38.61%
Value	[1],[2]	$ 689,625,330
Principal Value	[1],[2]	$ 690,000,000
Investment Interest Rate	[2]	0.89%
Investment Maturity Date	[2]	Jul. 27, 2017
Restricted for maintenance margin		$ 244,853,000
U.S. Treasury Bills, 0.960% due August 31, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	19.51%
Value	[1]	$ 348,475,104
Principal Value	[1]	$ 349,000,000
Investment Interest Rate		0.96%
Investment Maturity Date		Aug. 31, 2017
U.S. Treasury Bills, 0.990% due September 14, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[1]	4.36%
Value	[1]	$ 77,850,942
Principal Value	[1]	$ 78,000,000
Investment Interest Rate		0.99%
Investment Maturity Date		Sep. 14, 2017
United States Treasury Obligations [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		76.81%	[1]	93.99%	[3]
Value		$ 1,371,935,248	[1]	$ 2,403,838,023	[3]
Investments, cost		$ 1,371,851,699		$ 2,403,904,566
Exchange-Traded Fund - PowerShares Treasury Collateral Portfolio [Member] | Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[4],[5]	14.03%
Affiliated investments, at value	[4],[5]	$ 250,525,440
Shares	[4],[5]	2,372,400
Affiliated Investments, at Cost		$ 249,990,226
Money Market Mutual Fund - Premier U.S. Government Money Portfolio - Institutional Class [Member] | Affiliated Investments [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity		5.38%	[6]	5.13%	[7]
Affiliated investments, at value		$ 96,035,039	[6]	$ 131,029,805	[7]
Shares		96,035,039	[6]	131,029,805	[7]
Investment Interest Rate		0.86%		0.41%
Affiliated Investments, at Cost		$ 96,035,039		$ 131,029,805
U.S. Treasury Bills, 0.490% due January 19, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]			21.89%
Value	[3]			$ 559,898,640
Principal Value	[3]			$ 560,000,000
Investment Interest Rate				0.49%
Investment Maturity Date				Jan. 19, 2017
U.S. Treasury Bills, 0.485% due January 26, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]			18.61%
Value	[3]			$ 475,874,812
Principal Value	[3]			$ 476,000,000
Investment Interest Rate				0.485%
Investment Maturity Date				Jan. 26, 2017
U.S. Treasury Bills, 0.490% due March 2, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]			16.41%
Value	[3]			$ 419,678,700
Principal Value	[3]			$ 420,000,000
Investment Interest Rate				0.49%
Investment Maturity Date				Mar. 02, 2017
U.S. Treasury Bills, 0.530% due April 6, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3],[8]			22.61%
Value	[3],[8]			$ 578,219,508
Principal Value	[3],[8]			$ 579,000,000
Investment Interest Rate	[8]			0.53%
Investment Maturity Date	[8]			Apr. 06, 2017
Restricted for maintenance margin				$ 244,657,000
U.S. Treasury Bills, 0.625% due May 18, 2017 [Member]
Schedule of Investments [Line Items]
Percentage of Shareholders' Equity	[3]			14.47%
Value	[3]			$ 370,166,363
Principal Value	[3]			$ 371,000,000
Investment Interest Rate				0.625%
Investment Maturity Date				May 18, 2017

[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 $244,853,000 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] Affiliated company. The security and the Fund are affiliated by having the same investment adviser. See Note 8.

[5] Non-income producing security.

[6] The security and the Fund are advised by wholly-owned subsidiaries of Invesco Ltd. and are therefore considered to be affiliated. The rate shown is the 7-day SEC standardized yield as of June 30, 2017.

[7] The security and the Fund are advised by wholly-owned subsidiaries of Invesco Ltd. and are therefore considered to be affiliated. The rate shown is the 7-day SEC standardized yield as of December 31, 2016.

[8] United States Treasury Obligations of $244,657,000 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts.