State Street Real Estate Securities VIS Fund Investment Strategy - State Street Real Estate Securities VIS Fund	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Principal Investment Strategies</span>
Strategy Narrative [Text Block]	The Fund seeks to achieve its investment objective by investing at least 80% of its net assets (plus any borrowings for investment purposes) under normal circumstances in equity securities, such as common and preferred stocks, and debt securities of U.S. issuers that are principally engaged in or related to the real estate industry, including those that own significant real estate assets. Shareholders will receive sixty (60) days' notice prior to a change in the 80% investment policy. The Fund does not invest directly in real estate. The Fund considers an issuer to be “principally engaged in” or “principally related to” the real estate industry if at least 50% of its assets (marked-to-market), gross income or net profits are attributable to development, ownership, construction, management or sale of residential, commercial or industrial real estate, or to products or services related to the real estate industry. Issuers engaged in the real estate industry include equity real estate investment trusts (“REITs”), mort gage REITs, real estate brokers and developers, companies that manage real estate and companies that own substantial amounts of real estate. Issuers in businesses related to the real estate industry include manufacturers and distributors of building supplies and financial institutions that issue or service mortgages. The Fund also may invest to a lesser extent in equity securities and debt securities of issuers outside the real estate industry. The Fund also may invest up to 35% of its assets in high yield securities (also known as “junk bonds”) and up to 20% of its assets in foreign securities.

State Street Real Estate Securities VIS Fund Investment Strategy - State Street Real Estate Securities VIS Fund

Dec. 31, 2025

<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Principal Investment Strategies</span>

Strategy Narrative [Text Block]

The Fund seeks to achieve its investment objective by investing at least 80% of its net assets (plus any borrowings for investment purposes) under normal circumstances in equity securities, such as common and preferred stocks, and debt securities of U.S. issuers that are principally engaged in or related to the real estate industry, including those that own significant real estate assets. Shareholders will receive sixty (60) days' notice prior to a change in the 80% investment policy. The Fund does not invest directly in real estate. The Fund considers an issuer to be “principally engaged in” or “principally related to” the real estate industry if at least 50% of its assets (marked-to-market), gross income or net profits are attributable to development, ownership, construction, management or sale of residential, commercial or industrial real estate, or to products or services related to the real estate industry. Issuers engaged in the real estate industry include equity real estate investment trusts (“REITs”), mort gage REITs, real estate brokers and developers, companies that manage real estate and companies that own substantial amounts of real estate. Issuers in businesses related to the real estate industry include manufacturers and distributors of building supplies and financial institutions that issue or service mortgages. The Fund also may invest to a lesser extent in equity securities and debt securities of issuers outside the real estate industry. The Fund also may invest up to 35% of its assets in high yield securities (also known as “junk bonds”) and up to 20% of its assets in foreign securities.