Schedule of Investments (Unaudited) - Treasury Bills and Money Market Fund - USD ($) | 9 Months Ended | 12 Months Ended |
Sep. 30, 2018 | Dec. 31, 2017 |
Schedule Of Investments [Line Items] | | | | | |
Investments in Securities, cost | | $ 229,613,206 | | $ 283,534,397 | |
Percentage of Shareholders' Equity | | 120.86% | | 90.26% | |
Value | | $ 207,041,069 | | $ 244,408,079 | |
Affiliated investments, at value | | 22,546,692 | | 39,094,237 | |
Total Investments in Securities | | 229,587,761 | | 283,502,316 | |
Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Affiliated Investments, at Cost | | $ 22,535,208 | | $ 39,110,095 | |
Percentage of Shareholders' Equity | | 11.87% | | 12.45% | |
Affiliated investments, at value | | $ 22,546,692 | | $ 39,094,237 | |
U.S. Treasury Bills, 2.010% due November 8, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 2.01% | | | |
Investment Maturity Date | [1] | Nov. 8, 2018 | | | |
Percentage of Shareholders' Equity | [1] | 39.40% | | | |
Value | [1] | $ 74,836,521 | | | |
Principal Value | [1] | $ 75,000,000 | | | |
U.S. Treasury Bills, 2.095% due December 6, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[2] | 2.095% | | | |
Investment Maturity Date | [1],[2] | Dec. 6, 2018 | | | |
Restricted for maintenance margin | [1],[2] | $ 83,844,045 | | | |
Percentage of Shareholders' Equity | [1],[2] | 25.69% | | | |
Value | [1],[2] | $ 48,809,329 | | | |
Principal Value | [1],[2] | $ 49,000,000 | | | |
U.S. Treasury Bills, 2.175% due January 3, 2019 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[2] | 2.175% | | | |
Investment Maturity Date | [1],[2] | Jan. 3, 2019 | | | |
Restricted for maintenance margin | | $ 83,844,045 | | | |
Percentage of Shareholders' Equity | [1],[2] | 26.69% | | | |
Value | [1],[2] | $ 50,708,032 | | | |
Principal Value | [1],[2] | $ 51,000,000 | | | |
U.S. Treasury Bills, 2.210% due February 28, 2019 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[2] | 2.21% | | | |
Investment Maturity Date | [1],[2] | Feb. 28, 2019 | | | |
Restricted for maintenance margin | | $ 83,844,045 | | | |
Percentage of Shareholders' Equity | [1],[2] | 17.21% | | | |
Value | [1],[2] | $ 32,687,187 | | | |
Principal Value | [1],[2] | 33,000,000 | | | |
United States Treasury Obligations [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investments in Securities, cost | [1] | $ 207,077,998 | | $ 244,424,302 | |
Percentage of Shareholders' Equity | [1] | 108.99% | | 77.81% | |
Value | [1] | $ 207,041,069 | | $ 244,408,079 | |
Exchange-Traded Fund [Member] | Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Affiliated Investments, at Cost | [3] | $ 16,006,371 | | $ 16,006,371 | |
Percentage of Shareholders' Equity | [3] | 8.43% | | 5.09% | |
Affiliated investments, at value | [3] | $ 16,017,855 | | $ 15,990,513 | |
Shares | [3] | 151,900 | | 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 | | 1.95% | [4] | 1.15% | [5] |
Affiliated Investments, at Cost | | $ 6,528,837 | [4] | $ 23,103,724 | [5] |
Percentage of Shareholders' Equity | | 3.44% | [4] | 7.36% | [5] |
Affiliated investments, at value | | $ 6,528,837 | [4] | $ 23,103,724 | [5] |
Shares | | 6,528,837 | [4] | 23,103,724 | [5] |
A L P S Distributors Inc | Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Affiliated Investments, at Cost | | $ 22,535,208 | | | |
U.S. Treasury Bills, 1.180% due January 4, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | | | 1.18% | |
Investment Maturity Date | [1] | | | Jan. 4, 2018 | |
Percentage of Shareholders' Equity | [1] | | | 14.01% | |
Value | [1] | | | $ 43,997,241 | |
Principal Value | [1] | | | $ 44,000,000 | |
U.S. Treasury Bills, 1.285% due March 1, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[6] | | | 1.285% | |
Investment Maturity Date | [1],[6] | | | Mar. 1, 2018 | |
Restricted for maintenance margin | [1],[6] | | | $ 12,972,700 | |
Percentage of Shareholders' Equity | [1],[6] | | | 13.34% | |
Value | [1],[6] | | | $ 41,914,233 | |
Principal Value | [1],[6] | | | $ 42,000,000 | |
U.S. Treasury Bills, 1.245% due January 18, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | | | 1.245% | |
Investment Maturity Date | [1] | | | Jan. 18, 2018 | |
Percentage of Shareholders' Equity | [1] | | | 14.95% | |
Value | [1] | | | $ 46,974,228 | |
Principal Value | [1] | | | $ 47,000,000 | |
U.S. Treasury Bills, 1.285% due February 22, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | | | 1.285% | |
Investment Maturity Date | [1] | | | Feb. 22, 2018 | |
Percentage of Shareholders' Equity | [1] | | | 16.21% | |
Value | [1] | | | $ 50,908,965 | |
Principal Value | [1] | | | $ 51,000,000 | |
U.S. Treasury Bills, 1.450% due June 7, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | | | 1.45% | |
Investment Maturity Date | [1] | | | Jun. 7, 2018 | |
Percentage of Shareholders' Equity | [1] | | | 19.30% | |
Value | [1] | | | $ 60,613,412 | |
Principal Value | [1] | | | $ 61,000,000 | |
| |
[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 $83,844,045 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts. | |
[3] | Affiliated company. The security and the Fund are affiliated by having the same investment adviser. See Note 8. | |
[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 September 30, 2018. | |
[5] | 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. | |
[6] | United States Treasury Obligations of $12,972,700 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts. | |