v3.26.1
State Street Income VIS Fund Investment Risks - State Street Income VIS Fund
Dec. 31, 2025
Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Market Risk: The Fund's investments are subject to changes in general economic conditions, general market fluctuations and the risks inherent in investment in securities markets. Investment markets can be volatile and prices of investments can change substantially due to various factors including, but not limited to, economic growth or recession, changes in interest rates, inflation, changes in the actual or perceived creditworthiness of issuers, and general market liquidity. The Fund is subject to the risk that geopolitical events will disrupt securities markets and adversely affect global economies and markets. Local, regional or global events such as war, military conflicts, acts of terrorism, trade policy changes or disputes, the threat or actual imposition of tariffs, natural disasters, the spread of infectious illness or other public health issues, or other events could have a significant impact on the Fund and its investments.
Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Debt Securities Risk: The values of debt securities may increase or decrease as a result of the following: market fluctuations, changes in interest rates, actual or perceived inability or unwillingness of issuers, guarantors or liquidity providers to make scheduled principal or interest payments, or illiquidity in debt securities markets. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. A rising interest rate environment may cause the value of the Fund's fixed income securities to decrease, an adverse impact on the liquidity of the Fund's fixed income securities, and increased volatility of the fixed income markets. During periods when interest rates are at low levels, the Fund's yield can be low, and the Fund may have a negative yield (i.e., it may lose money on an operating basis). To the extent that interest rates fall, certain underlying obligations may be paid off substantially faster than originally anticipated. If the principal on a debt obligation is prepaid before expected, the prepayments of principal may have to be reinvested in obligations paying interest at lower rates. During periods of falling interest rates, the income received by the Fund may decline. Changes in interest rates will likely have a greater effect on the values of debt securities of longer durations. Returns on investments in debt securities could trail the returns on other investment options, including investments in equity securities. High levels of inflation and/or a significantly changing interest rate environment can lead to heightened levels of volatility and reduced liquidity.
Mortgage Related and Other Asset Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Mortgage-Related and Other Asset-Backed Securities Risk: Investments in mortgage-related and other asset-backed securities are subject to the risk of significant credit downgrades, illiquidity, and defaults to a greater extent than many other types of fixed-income investments. The liquidity of mortgage-related and asset-backed securities may change over time. During periods of falling interest rates, mortgage- and asset-backed securities may be called or prepaid, which may result in the Fund having to reinvest proceeds in other investments at a lower interest rate. During periods of rising interest rates, the average life of mortgage- and asset-backed securities may extend, which may lock in a below-market interest rate, increase the security's duration and interest rate sensitivity, and reduce the value of the security. Enforcing rights against the underlying assets or collateral may be difficult, and the underlying assets or collateral may be insufficient if the issuer defaults.
US Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] U.S. Government Securities Risk: Certain U.S. government securities are supported by the full faith and credit of the United States; others are supported by the right of the issuer to borrow from the U.S. Treasury; others are supported by the discretionary authority of the U.S. government to purchase the agency's obligations; and still others are supported only by the credit of the issuing agency, instrumentality, or enterprise. Although U.S. government-sponsored enterprises such as the Federal Home Loan Mortgage Corporation (“Freddie Mac”) and the Federal National Mortgage Association (“Fannie Mae”) may be chartered or sponsored by Congress, they are not funded by Congressional appropriations, and their securities are not issued by the U.S. Treasury, are not supported by the full faith and credit of the U.S. government, and involve increased credit risks.
Below Investment Grade Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Below Investment-Grade Securities Risk: Lower-quality debt securities (“high yield” or “junk” bonds) are considered predominantly speculative, and can involve a substantially greater risk of default than higher quality debt securities. Issuers of lower-quality debt securities may have substantially greater risk of insolvency or bankruptcy than issuers of higher-quality debt securities. They can be illiquid, and their values can have significant volatility and may decline significantly over short periods of time. Lower-quality debt securities tend to be more sensitive to adverse news about the issuer, or the market or economy in general.
Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Counterparty Risk: The Fund will be subject to credit risk with respect to the counterparties with which the Fund enters into derivatives contracts, repurchase agreements, reverse repurchase agreements, and other transactions. If a counterparty fails to meet its contractual obligations, the Fund may be unable to terminate or realize any gain on the investment or transaction, or to recover collateral posted to the counterparty, resulting in a loss to the Fund. If the Fund holds collateral posted by its counterparty, it may be delayed or prevented from realizing on the collateral in the event of a bankruptcy or insolvency proceeding relating to the counterparty.
Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Currency Risk: The value of the Fund's assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and delays, restrictions or prohibitions on the repatriation of foreign currencies. Foreign currency exchange rates may have significant volatility, and changes in the values of foreign currencies against the U.S. dollar may result in substantial declines in the values of the Fund's assets denominated in foreign currencies.
Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Derivatives Risk: Derivative transactions can create investment leverage and may have significant volatility. It is possible that a derivative transaction will result in a much greater loss than the principal amount invested, that changes in the value of a derivative transaction may not correlate perfectly with the underlying asset, and that the Fund may not be able to close out a derivative transaction at a favorable time or price. The counterparty to a derivatives contract may be unable or unwilling to make timely settlement payments, return the Fund's margin, or otherwise honor its obligations. A derivatives transaction may not behave in the manner anticipated by the Adviser or may not have the effect on the Fund anticipated by the Adviser.
Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Emerging Markets Risk: Risks of investing in emerging markets include, among others, greater political and economic instability, greater volatility in currency exchange rates, less developed securities markets, increased potential for market manipulation, possible trade barriers, currency transfer restrictions, a more limited number of potential buyers and issuers, an emerging market country's dependence on revenue from particular commodities or international aid, less governmental supervision and regulation, unavailability of currency hedging techniques, differences in auditing and financial reporting standards, less stringent investor protection and disclosure standards, less developed public health systems, and less developed legal systems. There is also the potential for unfavorable action such as expropriation, nationalization, embargoes, and acts of war. The securities of emerging market companies may trade less frequently and in smaller volumes than more widely held securities. Market disruptions or substantial market corrections may limit very significantly the liquidity of securities of certain companies in a particular country or geographic region, or of all companies in the country or region. The Fund may be unable to liquidate its positions in such securities at any time, or at a favorable price, in order to meet the Fund's obligations. These risks are generally greater for investments in frontier market countries, which typically have smaller economies or less developed capital markets than traditional emerging market countries.
Equity Investing Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Equity Investing Risk: The market prices of equity securities owned by the Fund may go up or down, sometimes rapidly or unpredictably. The value of a security may decline for a number of reasons that may directly relate to the issuer and also may decline due to general industry or market conditions that are not specifically related to a particular company. In addition, equity markets tend to move in cycles, which may cause stock prices to fall over short or extended periods of time.
Focused Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Focused Investment Risk: To the extent the Fund invests a large percentage of its assets in securities within the same country, state, region, or economic sector its investment strategy could result in more risk or greater volatility in returns than if the Fund's investments were less focused.
Large Transactions Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Large Transactions Risk: To the extent a large proportion of the shares of the Fund are held by a small number of shareholders (or a single shareholder), including funds or accounts over which the Adviser has investment discretion, the Fund is subject to the risk that these shareholders will purchase or redeem Fund Shares in large amounts rapidly or unexpectedly, including as a result of an asset allocation decision made by the Adviser. In addition, a large number of shareholders collectively may purchase or redeem Fund Shares in large amounts rapidly or unexpectedly (collectively, such transactions are referred to as “large shareholder transactions”). Large shareholder transactions could adversely affect the ability of the Fund to conduct its investment program.
Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Liquidity Risk: Lack of a ready market, stressed market conditions, or restrictions on resale may limit the ability of the Fund to sell a security at an advantageous time or price or at all. Illiquid investments may trade at a discount from comparable, more liquid investments and may be subject to wide fluctuations in market value. Illiquidity of the Fund's holdings may also limit the ability of the Fund to obtain cash to meet redemptions on a timely basis. In addition, the Fund, due to limitations on investments in any illiquid investments and/or the difficulty in purchasing and selling such investments, may be unable to achieve its desired level of exposure to a certain market or sector.
Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Management Risk: The Fund is actively managed. The Adviser's judgments about the attractiveness, relative value, or potential appreciation of a particular sector, security, commodity or investment strategy or as to a hedging strategy may prove to be incorrect, and may cause the Fund to incur losses. There can be no assurance that the Adviser's investment techniques and decisions will produce the desired results.
Municipal Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Municipal Obligations Risk: Issuers, including governmental issuers, may be unable to pay their obligations as they come due. The values of municipal obligations may be adversely affected by local political and economic conditions and developments. In addition, the values of municipal obligations that depend on a specific revenue source to fund their payment obligations may fluctuate as a result of actual or anticipated changes in the cash flows generated by the revenue source or changes in the priority of the municipal obligation to receive the cash flows generated by the revenue source. Municipal obligations may be more susceptible to downgrades or defaults during recessions or similar periods of economic stress. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund's ability to sell its municipal obligations at attractive prices, particularly in stressed market conditions. The differences between the price at which an obligation can be purchased and the price at which it can be sold may widen during periods of market distress. Less liquid obligations can become more difficult to value and be subject to erratic price movements. In addition, changes in U.S. federal tax laws or the activity of an issuer may adversely affect the tax-exempt status of municipal obligations. Loss of tax-exempt status may result in a significant decline in the values of such municipal obligations.
Non U S Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Non-U.S. Securities Risk: Non-U.S. securities (including depositary receipts) are subject to political, regulatory, and economic risks not present in domestic investments. There may be less information publicly available about a non-U.S. entity than about a U.S. entity, and many non-U.S. entities are not subject to accounting, auditing, legal and financial report standards comparable to those in the United States. Further, such entities and/or their securities may be subject to risks associated with currency controls; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. Foreign governments may impose restrictions on the repatriation of capital to the U.S. In addition, to the extent that the Fund buys securities denominated in a foreign currency, there are special risks such as changes in currency exchange rates and the risk that a foreign government could regulate foreign exchange transactions. In addition, to the extent investments are made in a limited number of countries, events in those countries will have a more significant impact on the Fund. Investments in depositary receipts may be less liquid and more volatile than the underlying shares in their primary trading market.
Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Portfolio Turnover Risk: Frequent purchases and sales of portfolio securities may result in higher Fund expenses.
Risk of Investment in Other Pools [Member]  
Prospectus [Line Items]  
Risk [Text Block] Risk of Investment in Other Pools: When the Fund invests in another pooled investment vehicle (e.g., a mutual fund or exchange-traded fund), it is exposed to the risk that the other pool will not perform as expected and is exposed indirectly to all of the risks applicable to an investment in such other pool. The investment policies of the other pool may not be the same as those of the Fund; as a result, an investment in the other pool may be subject to additional or different risks than those to which the Fund is typically subject. The Fund bears its proportionate share of the fees and expenses of any pool in which it invests. The Adviser or an affiliate may serve as investment adviser to a pool in which the Fund may invest, leading to potential conflicts of interest. It is possible that other clients of the Adviser or its affiliates will purchase or sell interests in a pool sponsored or managed by the Adviser or its affiliates at prices and at times more favorable than those at which the Fund does so.
Valuation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Valuation Risk: Certain portfolio holdings may be valued on the basis of factors other than market quotations. This may occur more often in times of market turmoil or reduced liquidity. There are multiple methods that can be used to value a portfolio holding when market quotations are not readily available. The value established for any portfolio holding at a point in time might differ from what would be produced using a different methodology or if it had been priced using market quotations. Portfolio holdings that are valued using techniques other than market quotations, including “fair valued” securities, may be subject to greater fluctuation in their valuations from one day to the next than if market quotations were used. In addition, there is no assurance that the Fund could sell or close out a portfolio position for the value established for it at any time, and it is possible that the Fund would incur a loss because a portfolio position is sold or closed out at a discount to the valuation established by the Fund at that time. Investors who purchase or redeem Fund Shares on days when the Fund is holding fair-valued investments may receive fewer or more shares or lower or higher redemption proceeds than they would have received if the Fund had not fair-valued the holding(s) or had used a different valuation methodology.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money by investing in the Fund.
Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is subject to investment risks, including possible loss of principal, is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation (“FDIC”) or any other government agency.