v3.26.1
State Street Moderate ETF Portfolio Investment Risks - State Street Moderate ETF Portfolio
Dec. 31, 2025
Underlying ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Underlying ETF Risk.  The investment performance of a Portfolio that invests all or substantially all of its assets in Underlying ETFs may be adversely affected if the Underlying ETFs are unable to meet their investment objectives or the Portfolio allocates a significant portion of its assets to an Underlying ETF that performs poorly, including relative to other Underlying ETFs. In addition, the Portfolio bears its pro-rata portion of the operating expenses of the Underlying ETFs in which it invests.
Asset Allocation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Asset Allocation Risk.  The Portfolio’s ability to achieve its investment objective depends upon the Subadviser’s analysis of various factors and the mix of asset classes that results from such analysis, which my prove incorrect. The particular asset allocation selected for the Portfolio may not perform as well as other asset allocations that could have been selected for the Portfolio. The Portfolio may experience losses or poor relative performance if the Subadviser allocates a significant portion of the Portfolio’s assets to an asset class that does not perform as the Subadviser anticipated, including relative to other asset classes. The Portfolio may underperform funds that allocate their assets differently than the Portfolio.
Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Portfolio Turnover Risk.  Portfolio turnover risk is both a direct and indirect risk of investing in the Portfolio. The investment techniques and strategies utilized by the Portfolio or the Underlying ETFs might result in a high degree of portfolio turnover. High portfolio turnover rates will increase the Portfolio’s or the Underlying ETFs’ transaction costs, which can adversely affect the returns on the Portfolio’s or the Underlying ETFs' performance.
Model and Data Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Model and Data Risk.  When the quantitative models (“Models”) and information and data (“Data”) used in managing the Portfolio contain an error, are input or designed incorrectly, or prove to be incorrect or incomplete, any investment decisions made in reliance on the Models and Data may not produce the desired results and the Portfolio may realize losses. Models may cause the Portfolio to underperform other investment strategies and may not perform as intended in volatile markets. In addition, any hedging based on faulty Models and Data may prove to be unsuccessful. Furthermore, the success of Models that are predictive in nature is dependent largely on the accuracy and reliability of the supplied historical data. All Models are susceptible to input errors which may cause the resulting information to be incorrect. Indirect risks of investing in the Portfolio (direct risks of investing in the Underlying ETFs) include:
Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Market Risk.  An Underlying ETF’s share price can fall because of, among other things, a decline in the market as a whole, deterioration in the prospects for a particular industry or company, changes in general economic conditions, such as prevailing interest rates or investor sentiment, or other factors including terrorism, war, natural disasters and the spread of infectious illness including epidemics or pandemics. In addition, unexpected political, regulatory, trade and diplomatic events within the United States and abroad may affect investor and consumer confidence and may adversely impact financial markets and the broader economy, perhaps suddenly and to a significant degree. Significant disruptions to the financial markets could adversely affect the liquidity and volatility of securities held by an Underlying ETF.
Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Foreign Investment Risk.  Investments in foreign securities, whether direct or indirect, tend to be more volatile and less liquid than investments in U.S. securities because, among other things, they involve risks relating to political, social, economic and other developments abroad, as well as risks resulting from differences between the regulations and reporting standards and practices to which U.S. and foreign issuers are subject. To the extent foreign securities are denominated in foreign currencies, their values may be adversely affected by changes in currency exchange rates.
Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Emerging Markets Risk.  In addition to all of the risks of investing in foreign developed markets, emerging market securities involve risks attendant to less mature and stable governments and economies, lower trading volume, trading suspension, security price volatility, proceeds repatriation restrictions, withholding and other taxes, some of which may be confiscatory, inflation, deflation, currency devaluation and adverse government regulations of industries or markets. As a result of these risks, the prices of emerging market securities tend to be more volatile than the securities of issuers located in developed markets.
Market Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Market Capitalization Risk.  Investing primarily in issuers in one market capitalization category (large, medium or small) carries the risk that due to current market conditions that category will be out of favor with investors. Larger, more established companies may be unable to respond quickly to new competitive challenges or attain the high growth rate of successful smaller companies. Stocks of medium and small capitalization companies may be more volatile than those of larger companies due to, among other things, narrower product lines, more limited financial resources and fewer experienced managers. In addition, there is typically less publicly available information about small capitalization companies, and their stocks may have a more limited trading market than stocks of larger companies.
Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Investment Style Risk.  Different investment styles such as growth or value tend to shift in and out of favor, depending on market and economic conditions as well as investor sentiment. An Underlying ETF may outperform or underperform other funds that employ a different investment style.
Credit and Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Credit and Counterparty Risk.  The value of an Underlying ETF’s investments may be adversely affected if a security’s credit rating is downgraded or an issuer of an investment held by an Underlying ETF fails to pay an obligation on a timely basis, otherwise defaults or is perceived by other investors to be less creditworthy. If a counterparty to a derivatives or other transaction with an Underlying ETF files for bankruptcy, becomes insolvent, or otherwise becomes unable or unwilling to honor its obligation to an Underlying ETF, the Underlying ETF may experience significant losses or delays in realizing income on or recovering collateral and may lose all or a part of the income from the transaction.
Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Interest Rate Risk.  The value of an Underlying ETF’s investments in fixed income securities may decline when prevailing interest rates rise or increase when interest rates fall. The longer a security’s maturity or duration, the greater its value will change in response to changes in interest rates. The interest earned on an Underlying ETF’s investments in fixed income securities may decline when prevailing interest rates fall. During periods of very low or negative interest rates, an Underlying ETF may be unable to maintain positive returns or pay dividends to Underlying ETF shareholders. Additionally, under certain market conditions in which interest rates are low or negative, an Underlying ETF may have a very low, or even negative yield. A low or negative yield would cause an Underlying ETF to lose money and the net asset value of the Underlying ETF’s shares to decline in certain conditions and over certain time periods. Changes in prevailing interest rates, particularly sudden changes, may also increase the level of volatility in fixed income and other markets, increase redemptions in an Underlying ETF’s shares and reduce the liquidity of an Underlying ETF’s debt securities and other income-producing holdings. Changes in interest rate levels are caused by a variety of factors, such as central bank monetary policies, inflation rates, and general economic and market conditions.
Loan Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Loan Investment Risk.  Investments by Underlying ETFs in loans expose the Portfolio to interest rate risk and the credit and counterparty risk of the underlying borrowers of those loans. No active trading market may exist for certain loans. Moreover, adverse market conditions may impair the liquidity of some actively traded loans. The Underlying ETF may have difficulty valuing and selling loans that are illiquid or are less actively traded. Loans are also subject to the risk that borrowers will prepay the principal more quickly than expected, which could cause the Underlying ETF to reinvest the repaid principal in investments with lower yields, thereby exposing the Portfolio to a lower rate of return. There may be a limited amount of public information about the loans in which the Underlying ETF invests. Purchases and sales of loans are generally subject to contractual restrictions that may impede the Underlying ETF’s ability to buy or sell loans and may negatively affect the transaction price. Loan transactions may take longer than seven days to settle, and the Underlying ETFs may hold cash, sell investments, or temporarily borrow from banks or other lenders in order to meet short-term liquidity needs. The Underlying ETF may not be entitled to rely on the anti-fraud protections of the federal securities laws with respect to any loans it owns in the event of fraud or misrepresentation by a borrower. The Underlying ETF’s purchase and sale of loans may involve the risk of market manipulation by a borrower. Any investments in below investment grade loans and other debt securities expose a portfolio to greater market risk and credit and counterparty risk than a portfolio that invests only in investment grade loans and debt securities. Lower rated securities also may be subject to greater price volatility than higher rated investments.
High Yield Debt Security Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] High Yield Debt Security Risk.  High yield debt securities, or “junk” bonds, may be more susceptible to market risk and credit and counterparty risk than investment grade debt securities because issuers of high yield debt securities are less secure financially and their securities are more sensitive to downturns in the economy. In addition, the secondary market for high yield debt securities may not be as liquid as that for higher rated debt securities. High-yield debt securities range from those for which the prospect for repayment of principal and interest is predominantly speculative to those which are currently in default on principal or interest payments or whose issuers are in bankruptcy.
Commodities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Commodities Risk.  Exposure to the commodities markets may subject an Underlying ETF to greater volatility than investments in traditional securities. The value of commodities and commodity-linked derivative instruments may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a particular industry or commodity. The ability of an Underlying ETF that intends to qualify as a regulated investment company to invest in commodity-linked derivative instruments may be limited by its intention to so qualify, and could adversely affect such Underlying ETF’s ability to so qualify.
Real Estate Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Real Estate Investment Risk.  Investments in real estate investment trusts and other real estate related securities may be adversely impacted by the performance of the real estate market generally or that of a particular sub-sector or geographic region.
TIPS and Inflation Linked Bonds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] TIPS and Inflation-Linked Bonds Risk.  The value of inflation-protected securities generally fluctuates in response to changes in real interest rates, which are in turn tied to the relationship between nominal interest rates and the rate of inflation. Therefore, if inflation were to rise at a faster rate than nominal interest rates, real interest rates would decline, leading to an increase in the value of inflation-protected securities. In contrast, if nominal interest rates increased at a faster rate than inflation, real interest rates would rise, leading to a decrease in the value of inflation-protected securities. When real interest rates are rising faster than nominal interest rates, inflation-indexed bonds, including Treasury Inflation Protected Securities, may experience greater losses than other fixed income securities with similar durations. The inflation-protected securities markets are generally much smaller and less liquid than the markets for nominal bonds from the same issuers and as such can suffer losses during times of economic stress or illiquidity.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money by investing in the Portfolio.
Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Portfolio through a Contract is not a deposit or obligation of, or guaranteed by, any bank, and is not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. Government.