Schedule of Investments (Unaudited) - Treasury Bills and Money Market Fund - USD ($) | 3 Months Ended | 12 Months Ended |
Mar. 31, 2018 | Dec. 31, 2017 |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | | 100.17% | | 99.15% | |
Value | | $ 38,790,856 | | $ 37,933,681 | |
Affiliated investments, at value | | 2,372,039 | | 2,095,110 | |
Total Investments in Securities | | 41,162,895 | | 40,028,791 | |
Investments in Securities, cost | | $ 41,171,037 | | $ 40,033,382 | |
U.S. Treasury Bills, 1.695% due May 3, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | 17.01% | | | |
Value | [1] | $ 6,990,231 | | | |
Principal Value | [1] | $ 7,000,000 | | | |
Investment Interest Rate | [1] | 1.695% | | | |
Investment Maturity Date | [1] | May 3, 2018 | | | |
U.S. Treasury Bills, 1.660% due June 7, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | 9.70% | | | |
Value | [1] | $ 3,987,851 | | | |
Principal Value | [1] | $ 4,000,000 | | | |
Investment Interest Rate | [1] | 1.66% | | | |
Investment Maturity Date | [1] | Jun. 7, 2018 | | | |
U.S. Treasury Bills, 1.740% due July 5, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1],[2] | 21.81% | | | |
Value | [1],[2] | $ 8,959,924 | | | |
Principal Value | [1],[2] | $ 9,000,000 | | | |
Investment Interest Rate | [1],[2] | 1.74% | | | |
Investment Maturity Date | [1],[2] | Jul. 5, 2018 | | | |
Restricted for maintenance margin | | $ 2,986,500 | | | |
U.S. Treasury Bills, 1.830% due August 30, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | 45.88% | | | |
Value | [1] | $ 18,852,850 | | | |
Principal Value | [1] | $ 19,000,000 | | | |
Investment Interest Rate | [1] | 1.83% | | | |
Investment Maturity Date | [1] | Aug. 30, 2018 | | | |
United States Treasury Obligations [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | 94.40% | | 93.96% | |
Value | [1] | $ 38,790,856 | | $ 37,933,681 | |
Investments in Securities, cost | [1] | $ 38,798,998 | | $ 37,938,272 | |
Money Market Mutual Fund - Invesco Premier U.S. Government Money Portfolio - Institutional Class [Member] | Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | | 5.77% | [3] | 5.19% | [4] |
Affiliated investments, at value | | $ 2,372,039 | [3] | $ 2,095,110 | [4] |
Shares | | 2,372,039 | [3] | 2,095,110 | [4] |
Investment Interest Rate | | 1.52% | [3] | 1.15% | [4] |
Investments in Securities, cost | | $ 2,372,039 | [3] | $ 2,095,110 | [4] |
U.S. Treasury Bills, 1.180% due January 4, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 22.29% | |
Value | [1] | | | $ 8,999,436 | |
Principal Value | [1] | | | $ 9,000,000 | |
Investment Interest Rate | [1] | | | 1.18% | |
Investment Maturity Date | [1] | | | Jan. 4, 2018 | |
U.S. Treasury Bills, 1.285% due February 22, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 19.78% | |
Value | [1] | | | $ 7,985,720 | |
Principal Value | [1] | | | $ 8,000,000 | |
Investment Interest Rate | [1] | | | 1.285% | |
Investment Maturity Date | [1] | | | Feb. 22, 2018 | |
U.S. Treasury Bills, 1.285% due March 1, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1],[5] | | | 46.97% | |
Value | [1],[5] | | | $ 18,961,200 | |
Principal Value | [1],[5] | | | $ 19,000,000 | |
Investment Interest Rate | [1],[5] | | | 1.285% | |
Investment Maturity Date | [1],[5] | | | Mar. 1, 2018 | |
Restricted for maintenance margin | | | | $ 2,993,700 | |
U.S. Treasury Bills, 1.450% due June 7, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 4.92% | |
Value | [1] | | | $ 1,987,325 | |
Principal Value | [1] | | | $ 2,000,000 | |
Investment Interest Rate | [1] | | | 1.45% | |
Investment Maturity Date | [1] | | | Jun. 7, 2018 | |
| |
[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 $2,986,500 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts. | |
[3] | 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 March 31, 2018. | |
[4] | 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, 2017. | |
[5] | United States Treasury Obligations of $2,993,700 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts. | |