| Derivative Instruments and Hedging Activities Disclosure [Text Block] |
| 9 - | Investing in Index Futures |
Substantially all of the Trust’s assets are invested in Index Futures. The Index Futures’ settlement value at expiration is based on the value of the S&P GSCI-ER at that time. Therefore, the value of the Trust will fluctuate based upon the value of the S&P GSCI-ER and the prices of futures contracts and commodities underlying the S&P GSCI-ER. The commodities markets have historically been extremely volatile. For the nine months ended September 30, 2026 and the year ended December 31, 2025, the average month-end notional amounts of open Index Futures were $970,666,678 and $1,010,924,315, respectively.
The following table shows the variation margin on open futures contracts, by risk exposure category, on the Statements of Assets and Liabilities as of September 30, 2026 and December 31, 2025:
| | | Asset Derivatives | | Fair Value | | Liability Derivatives | | Fair Value | |
| September 30, 2026 | | | | | | | | | | | |
| Commodity contracts | | Receivable for variation margin on open futures contracts | | $ | 10,586,199 | | Payable for variation margin on open futures contracts | | $ | — | |
| December 31, 2025 | | | | | | | | | | | |
| Commodity contracts | | Receivable for variation margin on open futures contracts | | $ | — | | Payable for variation margin on open futures contracts | | $ | 11,332,892 | |
The following table shows the effect of the open futures contracts, by risk exposure category, on the Statements of Operations for the three and nine months ended September 30, 2026 and 2025:
| | | Statements of
Operations Location | | Net Realized
Gain (Loss) | | | Net Change in Unrealized
Appreciation/Depreciation | |
| Three Months Ended September 30, 2026 | | | | | | | | | | |
| Commodity contracts | | Net realized gain (loss) from futures contracts | | $ | 114,685,407 | | | $ | — | |
| | | Net change in unrealized appreciation (depreciation) on futures contracts | | | — | | | | 84,736,873 | |
| Three Months Ended September 30, 2025 | | | | | | | | | | |
| Commodity contracts | | Net realized gain (loss) from futures contracts | | $ | 17,956,102 | | | $ | — | |
| | | Net change in unrealized appreciation (depreciation) on futures contracts | | | — | | | | 11,839,522 | |
| Nine Months Ended September 30, 2026 | | | | | | | | | | |
| Commodity contracts | | Net realized gain (loss) from futures contracts | | $ | 373,712,545 | | | $ | — | |
| | | Net change in unrealized appreciation (depreciation) on futures contracts | | | — | | | | 3,820,278 | |
| Nine Months Ended September 30, 2025 | | | | | | | | | | |
| Commodity contracts | | Net realized gain (loss) from futures contracts | | $ | 48,119,207 | | | $ | — | |
| | | Net change in unrealized appreciation (depreciation) on futures contracts | | | — | | | | (25,642,257 | ) |
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