| Label | Element | Value |
|---|---|---|
| Risk Return Abstract | rr_RiskReturnAbstract | |
| Registrant Name | dei_EntityRegistrantName | STATE STREET INSTITUTIONAL INVESTMENT TRUST |
| Prospectus Date | rr_ProspectusDate | Dec. 31, 2024 |
| Document Creation Date | dei_DocumentCreationDate | Dec. 19, 2024 |