Schedule of Investments (Unaudited) - Treasury Bills and Money Market Fund - USD ($) | 9 Months Ended | 12 Months Ended |
Sep. 30, 2017 | Dec. 31, 2016 |
Schedule Of Investments [Line Items] | | | | | |
Investments, cost | | $ 237,777,650 | | $ 271,949,512 | |
Percentage of Shareholders' Equity | | 82.22% | | 95.71% | |
Value | | $ 207,520,816 | | $ 252,671,516 | |
Affiliated investments, at value | | 30,340,771 | | 19,276,827 | |
Total Investments in Securities | | 237,861,587 | | 271,948,343 | |
Affiliated Investments [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Affiliated Investments, at Cost | | $ 30,268,527 | | 19,276,827 | |
Percentage of Shareholders' Equity | | 10.49% | | | |
Affiliated investments, at value | | $ 30,340,771 | | | |
U.S. Treasury Bills, 0.970% due October 26, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 0.97% | | | |
Investment Maturity Date | [1] | Oct. 26, 2017 | | | |
Percentage of Shareholders' Equity | [1] | 10.36% | | | |
Value | [1] | $ 29,981,375 | | | |
Principal Value | [1] | $ 30,000,000 | | | |
U.S. Treasury Bills, 1.000% due November 24, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 1.00% | | | |
Investment Maturity Date | [1] | Nov. 24, 2017 | | | |
Percentage of Shareholders' Equity | [1] | 18.64% | | | |
Value | [1] | $ 53,921,360 | | | |
Principal Value | [1] | $ 54,000,000 | | | |
U.S. Treasury Bills, 1.020% due December 7, 2017 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 1.02% | | | |
Investment Maturity Date | [1] | Dec. 7, 2017 | | | |
Percentage of Shareholders' Equity | [1] | 13.11% | | | |
Value | [1] | $ 37,931,727 | | | |
Principal Value | [1] | $ 38,000,000 | | | |
U.S. Treasury Bills, 1.050% due January 4, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1],[2] | 1.05% | | | |
Investment Maturity Date | [1],[2] | Jan. 4, 2018 | | | |
Restricted for maintenance margin | [1],[2] | $ 17,951,400 | | | |
Percentage of Shareholders' Equity | [1],[2] | 15.17% | | | |
Value | [1],[2] | $ 43,881,917 | | | |
Principal Value | [1],[2] | $ 44,000,000 | | | |
U.S. Treasury Bills, 1.115% due March 1, 2018 [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investment Interest Rate | [1] | 1.115% | | | |
Investment Maturity Date | [1] | Mar. 1, 2018 | | | |
Percentage of Shareholders' Equity | [1] | 14.45% | | | |
Value | [1] | $ 41,804,437 | | | |
Principal Value | [1] | 42,000,000 | | | |
United States Treasury Obligations [Member] | | | | | |
Schedule Of Investments [Line Items] | | | | | |
Investments, cost | | $ 207,509,123 | [1] | $ 252,672,685 | [3] |
Percentage of Shareholders' Equity | | 71.73% | [1] | 88.93% | [3] |
Value | | $ 207,520,816 | [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] | 5.56% | | | |
Affiliated investments, at value | [4],[5] | $ 16,078,615 | | | |
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 | | 0.92% | [6] | 0.41% | [7] |
Affiliated Investments, at Cost | | $ 14,262,156 | [6] | $ 19,276,827 | [7] |
Percentage of Shareholders' Equity | | 4.93% | [6] | 6.78% | [7] |
Affiliated investments, at value | | $ 14,262,156 | [6] | $ 19,276,827 | [7] |
Shares | | 14,262,156 | [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],[8] | | | 17.59% | |
Value | [3],[8] | | | $ 49,986,850 | |
Principal Value | [3],[8] | | | $ 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 $17,951,400 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 September 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. | |