State Street US Equity VIS Fund Investment Strategy - State Street US Equity 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 of U.S. companies, such as common and preferred stocks. The Fund considers a company to be a U.S. company if it generates at least 50% of its revenues or profits from business activities in the U.S., has at least 50% of its assets situated in the U.S., or has the principal trading market for its securities in the U.S. The Fund is designed to produce a broadly diversified portfolio, and typically has characteristics similar to the S&P 500® Index, including average market capitalization and dividend yield potential. At times, the Fund's investments may be focused in one or more market sectors, such as information technology. Through fundamental company research involving analyzing financial statements and other information about a company, SSGA Funds Management, Inc. (“SSGA FM” or the “Adviser”), the Fund's investment adviser, primarily seeks to identify securities of large and medium sized companies (meaning companies with market capitalizations of $2 billion or more) that they believe have desirable characteristics for the Fund such as: •low valuations in relation to their peers, the market, their historical valuations or their growth rate potential; •appropriate capital structures; and/or •high quality management focused on generating shareholder value. The Adviser may consider selling a security when one of these characteristics no longer applies, when the Adviser believes that the valuation has become excessive, or when more attractive alternatives are identified. The Fund also may invest up to 15% of its net assets (plus any borrowings for investment purposes) in foreign securities and up to 20% of its net assets (plus any borrowings for investment purposes) in debt securities. The Adviser may also use various types of derivative instruments (such as futures contracts, options and forward contracts) to gain or hedge exposure to certain types of securities as an alternative to investing directly in or selling such securities.

State Street US Equity VIS Fund Investment Strategy - State Street US Equity 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 of U.S. companies, such as common and preferred stocks. The Fund considers a company to be a U.S. company if it generates at least 50% of its revenues or profits from business activities in the U.S., has at least 50% of its assets situated in the U.S., or has the principal trading market for its securities in the U.S. The Fund is designed to produce a broadly diversified portfolio, and typically has characteristics similar to the S&P 500® Index, including average market capitalization and dividend yield potential. At times, the Fund's investments may be focused in one or more market sectors, such as information technology. Through fundamental company research involving analyzing financial statements and other information about a company, SSGA Funds Management, Inc. (“SSGA FM” or the “Adviser”), the Fund's investment adviser, primarily seeks to identify securities of large and medium sized companies (meaning companies with market capitalizations of $2 billion or more) that they believe have desirable characteristics for the Fund such as: •low valuations in relation to their peers, the market, their historical valuations or their growth rate potential; •appropriate capital structures; and/or •high quality management focused on generating shareholder value. The Adviser may consider selling a security when one of these characteristics no longer applies, when the Adviser believes that the valuation has become excessive, or when more attractive alternatives are identified. The Fund also may invest up to 15% of its net assets (plus any borrowings for investment purposes) in foreign securities and up to 20% of its net assets (plus any borrowings for investment purposes) in debt securities. The Adviser may also use various types of derivative instruments (such as futures contracts, options and forward contracts) to gain or hedge exposure to certain types of securities as an alternative to investing directly in or selling such securities.