| Document And Entity Information | Jun. 30, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | iShares® S&P GSCI™ Commodity-Indexed Trust |
| Document, Type | 8-K |
| Document, Period End Date | Jun. 30, 2021 |
| Entity, Incorporation, State or Country Code | NY |
| Entity, File Number | 001-32947 |
| Entity, Tax Identification Number | 51-6573369 |
| Entity, Address, Address Line One | 400 Howard Street |
| Entity, Address, City or Town | San Francisco |
| Entity, Address, State or Province | CA |
| Entity, Address, Postal Zip Code | 94105 |
| City Area Code | 415 |
| Local Phone Number | 670-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Shares |
| Trading Symbol | GSG |
| Security Exchange Name | NYSEArca |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001332174 |
