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] | | | | | |
Investments, cost | | $ 185,269,912 | | $ 271,949,512 | |
Percentage of Shareholders' Equity | | 88.77% | | 95.71% | |
Value | | $ 162,821,089 | | $ 252,671,516 | |
Affiliated investments, at value | | 22,497,214 | | 19,276,827 | |
Total Investments | | 185,318,303 | | 271,948,343 | |
Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Affiliated Investments, at Cost | | $ 22,462,945 | | 19,276,827 | |
Percentage of Shareholders' Equity | | 10.78% | | | |
Affiliated investments, at value | | $ 22,497,214 | | | |
U.S. Treasury Bills, 0.840% due July 6, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 0.84% | | | |
Investment Maturity Date | [1] | Jul. 6, 2017 | | | |
Percentage of Shareholders' Equity | [1] | 11.50% | | | |
Value | [1] | $ 23,998,488 | | | |
Principal Value | [1] | $ 24,000,000 | | | |
U.S. Treasury Bills, 0.890% due July 27, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[2] | 0.89% | | | |
Investment Maturity Date | [1],[2] | Jul. 27, 2017 | | | |
Restricted for maintenance margin | [2] | $ 17,989,200 | | | |
Percentage of Shareholders' Equity | [1] | 24.89% | | | |
Value | [1] | $ 51,971,764 | | | |
Principal Value | [1] | $ 52,000,000 | | | |
U.S. Treasury Bills, 0.960% due August 31, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[2] | 0.96% | | | |
Investment Maturity Date | [1],[2] | Aug. 31, 2017 | | | |
Percentage of Shareholders' Equity | [1] | 20.09% | | | |
Value | [1] | $ 41,936,832 | | | |
Principal Value | [1] | $ 42,000,000 | | | |
U.S. Treasury Bills, 0.990% due September 14, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 0.99% | | | |
Investment Maturity Date | [1] | Sep. 14, 2017 | | | |
Percentage of Shareholders' Equity | [1] | 21.51% | | | |
Value | [1] | $ 44,914,005 | | | |
Principal Value | [1] | 45,000,000 | | | |
United States Treasury Obligations [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investments, cost | | $ 162,806,967 | [1] | $ 252,672,685 | [3] |
Percentage of Shareholders' Equity | | 77.99% | [1] | 88.93% | [3] |
Value | | $ 162,821,089 | [1] | $ 252,671,516 | [3] |
Exchange-Traded Fund - PowerShares Treasury Collateral Portfolio [Member] | Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Affiliated Investments, at Cost | [4],[5] | $ 16,006,371 | | | |
Percentage of Shareholders' Equity | [4],[5] | 7.69% | | | |
Affiliated investments, at value | [4],[5] | $ 16,040,640 | | | |
Shares | [4],[5] | 151,900 | | | |
Money Market Mutual Fund - Premier U.S. Government Money Portfolio - Institutional Class [Member] | Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | | 0.86% | [6] | 0.41% | [7] |
Affiliated Investments, at Cost | | $ 6,456,574 | [6] | $ 19,276,827 | [7] |
Percentage of Shareholders' Equity | | 3.09% | [6] | 6.78% | [7] |
Affiliated investments, at value | | $ 6,456,574 | [6] | $ 19,276,827 | [7] |
Shares | | 6,456,574 | [6] | 19,276,827 | [7] |
U.S. Treasury Bills, 0.490% due January 19, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [3] | | | 0.49% | |
Investment Maturity Date | [3] | | | Jan. 19, 2017 | |
Percentage of Shareholders' Equity | [3] | | | 4.93% | |
Value | [3] | | | $ 13,997,466 | |
Principal Value | [3] | | | $ 14,000,000 | |
U.S. Treasury Bills, 0.485% due January 26, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [3],[8] | | | 0.485% | |
Investment Maturity Date | [3],[8] | | | Jan. 26, 2017 | |
Restricted for maintenance margin | [8] | | | $ 31,990,400 | |
Percentage of Shareholders' Equity | [3] | | | 17.59% | |
Value | [3] | | | $ 49,986,850 | |
Principal Value | [3] | | | $ 50,000,000 | |
U.S. Treasury Bills, 0.475% due February 2, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [3] | | | 0.475% | |
Investment Maturity Date | [3] | | | Feb. 2, 2017 | |
Percentage of Shareholders' Equity | [3] | | | 1.76% | |
Value | [3] | | | $ 4,998,265 | |
Principal Value | [3] | | | $ 5,000,000 | |
U.S. Treasury Bills, 0.490% due March 2, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [3] | | | 0.49% | |
Investment Maturity Date | [3] | | | Mar. 2, 2017 | |
Percentage of Shareholders' Equity | [3] | | | 15.12% | |
Value | [3] | | | $ 42,967,105 | |
Principal Value | [3] | | | $ 43,000,000 | |
U.S. Treasury Bills, 0.530% due April 6, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [3] | | | 0.53% | |
Investment Maturity Date | [3] | | | Apr. 6, 2017 | |
Percentage of Shareholders' Equity | [3] | | | 15.12% | |
Value | [3] | | | $ 42,942,036 | |
Principal Value | [3] | | | $ 43,000,000 | |
U.S. Treasury Bills, 0.625% due May 18, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [3] | | | 0.625% | |
Investment Maturity Date | [3] | | | May 18, 2017 | |
Percentage of Shareholders' Equity | [3] | | | 34.41% | |
Value | [3] | | | $ 97,779,794 | |
Principal Value | [3] | | | $ 98,000,000 | |
| |
[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 $17,989,200 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 $31,990,400 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts. | |