Schedule of Investments (Unaudited) - Treasury Bills and Affiliated Investments - USD ($) | 3 Months Ended | 12 Months Ended |
Mar. 31, 2018 | Dec. 31, 2017 |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | | 96.39% | | 98.81% | |
Value | | $ 313,127,550 | | $ 311,472,491 | |
Affiliated Investments, at Value | | 18,374,970 | | 17,412,477 | |
Total Investments in Securities | | 331,502,520 | | 328,884,968 | |
Investments in Securities, cost | | $ 331,549,286 | | $ 328,926,740 | |
Affiliated Investments [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | | 5.35% | | 5.23% | |
Affiliated Investments, at Value | | $ 18,374,970 | | $ 17,412,477 | |
Affiliated Investments, at Cost | | $ 18,360,454 | | $ 17,417,436 | |
U.S. Treasury Bills, 1.695% due May 3, 2018 [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | 7.84% | | | |
Value | [1] | $ 26,962,318 | | | |
Principal Value | [1] | $ 27,000,000 | | | |
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] | 13.62% | | | |
Value | [1] | $ 46,857,242 | | | |
Principal Value | [1] | $ 47,000,000 | | | |
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] | 15.34% | | | |
Value | [1],[2] | $ 52,763,999 | | | |
Principal Value | [1],[2] | $ 53,000,000 | | | |
Investment Interest Rate | [1],[2] | 1.74% | | | |
Investment Maturity Date | [1],[2] | Jul. 5, 2018 | | | |
Restricted for maintenance margin | | $ 39,820,000 | | | |
U.S. Treasury Bills, 1.830% due August 30, 2018 [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | 54.24% | | | |
Value | [1] | $ 186,543,991 | | | |
Principal Value | [1] | $ 188,000,000 | | | |
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] | 91.04% | | 93.58% | |
Value | [1] | $ 313,127,550 | | $ 311,472,491 | |
Investments in Securities, cost | [1] | $ 313,188,832 | | $ 311,509,304 | |
Exchange-Traded Fund - PowerShares Treasury Collateral Portfolio [Member] | Affiliated Investments [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [3] | 1.46% | | 1.50% | |
Affiliated Investments, at Value | [3] | $ 5,019,800 | | $ 5,000,325 | |
Affiliated Investments, Shares | [3] | 47,500 | | 47,500 | |
Affiliated Investments, at Cost | [3] | $ 5,005,284 | | $ 5,005,284 | |
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 | | 3.89% | [4] | 3.73% | [5] |
Affiliated Investments, at Value | | $ 13,355,170 | [4] | $ 12,412,152 | [5] |
Affiliated Investments, Shares | | 13,355,170 | [4] | 12,412,152 | [5] |
Investment Interest Rate | | 1.52% | [4] | 1.15% | [5] |
Affiliated Investments, at Cost | | $ 13,355,170 | [4] | $ 12,412,152 | [5] |
U.S. Treasury Bills, 1.180% due January 4, 2018 [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 15.92% | |
Value | [1] | | | $ 52,996,676 | |
Principal Value | [1] | | | $ 53,000,000 | |
Investment Interest Rate | [1] | | | 1.18% | |
Investment Maturity Date | [1] | | | Jan. 4, 2018 | |
U.S. Treasury Bills, 1.245% due January 18, 2018 [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 2.70% | |
Value | [1] | | | $ 8,995,065 | |
Principal Value | [1] | | | $ 9,000,000 | |
Investment Interest Rate | [1] | | | 1.245% | |
Investment Maturity Date | [1] | | | Jan. 18, 2018 | |
U.S. Treasury Bills, 1.285% due February 22, 2018 [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 24.89% | |
Value | [1] | | | $ 82,851,845 | |
Principal Value | [1] | | | $ 83,000,000 | |
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],[6] | | | 47.98% | |
Value | [1],[6] | | | $ 159,673,267 | |
Principal Value | [1],[6] | | | $ 160,000,000 | |
Investment Interest Rate | [1],[6] | | | 1.285% | |
Investment Maturity Date | [1],[6] | | | Mar. 1, 2018 | |
Restricted for maintenance margin | | | | $ 39,916,000 | |
U.S. Treasury Bills, 1.450% due June 7, 2018 [Member] | | | | | |
Schedule of Investments [Line Items] | | | | | |
Percentage of Shareholders' Equity | [1] | | | 2.09% | |
Value | [1] | | | $ 6,955,638 | |
Principal Value | [1] | | | $ 7,000,000 | |
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 $39,820,000 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 March 31, 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 $39,916,000 are on deposit with the Commodity Broker and held as maintenance margin for open futures contracts. | |