State Street Emerging Markets Enhanced Index Portfolio Investment Strategy - State Street Emerging Markets Enhanced Index Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#000000;font-family:Times New Roman;font-size:11.5pt;font-weight:bold;">Principal Investment Strategies</span>
Strategy Narrative [Text Block]	SSGA Funds Management, Inc. (“SSGA FM” or “Subadviser”), subadviser to the Portfolio, uses in-depth quantitative investment analysis to construct a portfolio that it believes has the potential to outperform the MSCI Emerging Markets Index (the “Index”). SSGA FM invests the Portfolio’s assets primarily in equity securities of companies in the Index. As of the date of this Prospectus, the Index consists of large and mid capitalization companies in 24 emerging market countries. Under normal circumstances, the Portfolio invests at least 80% of its net assets in equity securities included in an emerging markets stock index. Investments in exchange-traded funds (“ETFs”), other investment companies and depositary receipts that provide exposure to equity securities included in an emerging markets stock index will count toward satisfaction of the foregoing policy. The Portfolio may invest in securities of any market capitalization, including securities of smaller capitalization companies. In addition, the Portfolio may pursue its investment objective and principal investment strategies by investing in ETFs, other investment companies and depositary receipts. The Portfolio may do so when such exposures represent an efficient way to gain a desired investment exposure, when investing directly in a market or country may be impractical, or for other investment purposes. The Portfolio is not a traditional “indexed investment.” Although the Portfolio typically seeks to maintain overall sector, country, region and industry exposures similar to those of the Index, because the Portfolio is actively managed and seeks to outperform the Index, its portfolio will differ from the Index and its return will typically differ from (and may underperform) the Index’s return. SSGA FM selects investments for the Portfolio based on its analysis of companies, focusing on factors such as relative valuations, the quality of a company’s earnings, the company’s balance sheet and cash flows, and investor sentiment. SSGA FM also incorporates into its proprietary quantitative model an evaluation of the macroeconomic and market risk environment, to take into account prevailing market conditions. This process seeks to maintain a disciplined approach that is adaptive to the macroeconomic environment and responsive to changing market conditions. SSGA FM may also attempt to identify companies, industries, or countries that SSGA FM believes have the potential to experience significant increases in market prices due to recently implemented or anticipated changes in a company, industry, or within a country. SSGA FM may purchase, sell, or continue to hold an investment for the Portfolio whenever it believes that doing so may benefit the Portfolio, on the basis of any of the factors described above or any other factors it deems relevant. From time to time, the Subadviser may make a qualitative judgment not to implement fully the results of the quantitative investment process if it believes that the process did not take into account all of the information relevant to a particular investment or the Portfolio in the aggregate, or that a different investment might be more appropriate. The Portfolio is unlikely to own all of the companies included in the Index and the Portfolio may invest a portion of its assets in securities not included in the Index. Equity securities in which the Portfolio may invest include common stocks and preferred stocks, real estate investment trusts, as well as derivatives selected by SSGA FM to attempt to provide a return comparable to the investment return of equity securities in the Index. The Portfolio may purchase securities in their initial public offerings. The Portfolio may invest in securities of companies in any market sector. In seeking to maintain overall sector, country, region and industry exposures similar to those of the Index, the Portfolio may, from time to time, focus its investments in one or more sectors, countries, regions or industries. The Portfolio may concentrate its investments (i.e., invest more than 25% of the value of its total assets) in securities of issuers in any industry only when its underlying index concentrates in that industry. The Portfolio will not otherwise concentrate its investments in securities of issuers in any industry.

State Street Emerging Markets Enhanced Index Portfolio Investment Strategy - State Street Emerging Markets Enhanced Index Portfolio

Dec. 31, 2025

<span style="color:#000000;font-family:Times New Roman;font-size:11.5pt;font-weight:bold;">Principal Investment Strategies</span>

Strategy Narrative [Text Block]

SSGA Funds Management, Inc. (“SSGA FM” or “Subadviser”), subadviser to the Portfolio, uses in-depth quantitative investment analysis to construct a portfolio that it believes has the potential to outperform the MSCI Emerging Markets Index (the “Index”). SSGA FM invests the Portfolio’s assets primarily in equity securities of companies in the Index. As of the date of this Prospectus, the Index consists of large and mid capitalization companies in 24 emerging market countries. Under normal circumstances, the Portfolio invests at least 80% of its net assets in equity securities included in an emerging markets stock index. Investments in exchange-traded funds (“ETFs”), other investment companies and depositary receipts that provide exposure to equity securities included in an emerging markets stock index will count toward satisfaction of the foregoing policy. The Portfolio may invest in securities of any market capitalization, including securities of smaller capitalization companies. In addition, the Portfolio may pursue its investment objective and principal investment strategies by investing in ETFs, other investment companies and depositary receipts. The Portfolio may do so when such exposures represent an efficient way to gain a desired investment exposure, when investing directly in a market or country may be impractical, or for other investment purposes. The Portfolio is not a traditional “indexed investment.” Although the Portfolio typically seeks to maintain overall sector, country, region and industry exposures similar to those of the Index, because the Portfolio is actively managed and seeks to outperform the Index, its portfolio will differ from the Index and its return will typically differ from (and may underperform) the Index’s return. SSGA FM selects investments for the Portfolio based on its analysis of companies, focusing on factors such as relative valuations, the quality of a company’s earnings, the company’s balance sheet and cash flows, and investor sentiment. SSGA FM also incorporates into its proprietary quantitative model an evaluation of the macroeconomic and market risk environment, to take into account prevailing market conditions. This process seeks to maintain a disciplined approach that is adaptive to the macroeconomic environment and responsive to changing market conditions. SSGA FM may also attempt to identify companies, industries, or countries that SSGA FM believes have the potential to experience significant increases in market prices due to recently implemented or anticipated changes in a company, industry, or within a country. SSGA FM may purchase, sell, or continue to hold an investment for the Portfolio whenever it believes that doing so may benefit the Portfolio, on the basis of any of the factors described above or any other factors it deems relevant. From time to time, the Subadviser may make a qualitative judgment not to implement fully the results of the quantitative investment process if it believes that the process did not take into account all of the information relevant to a particular investment or the Portfolio in the aggregate, or that a different investment might be more appropriate. The Portfolio is unlikely to own all of the companies included in the Index and the Portfolio may invest a portion of its assets in securities not included in the Index. Equity securities in which the Portfolio may invest include common stocks and preferred stocks, real estate investment trusts, as well as derivatives selected by SSGA FM to attempt to provide a return comparable to the investment return of equity securities in the Index. The Portfolio may purchase securities in their initial public offerings. The Portfolio may invest in securities of companies in any market sector. In seeking to maintain overall sector, country, region and industry exposures similar to those of the Index, the Portfolio may, from time to time, focus its investments in one or more sectors, countries, regions or industries. The Portfolio may concentrate its investments (i.e., invest more than 25% of the value of its total assets) in securities of issuers in any industry only when its underlying index concentrates in that industry. The Portfolio will not otherwise concentrate its investments in securities of issuers in any industry.