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Risk Return Abstract |
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Registrant Name |
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STATE STREET INSTITUTIONAL INVESTMENT TRUST
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Prospectus Date |
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Apr. 30, 2025
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State Street Target Retirement 2025 Fund |
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Risk Return Abstract |
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Risk/Return [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;text-transform:uppercase;">State Street Target Retirement 2025 Fund</span>
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Objective [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Investment Objective</span>
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Objective, Primary [Text Block] |
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The investment objective of the State Street Target Retirement 2025 Fund (the “Target Retirement 2025 Fund” or the “Fund”) is to seek capital growth and income over the long term.
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Expense [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Fees and Expenses of the Fund</span>
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Expense Narrative [Text Block] |
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The tables below describe the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund (“Fund Shares”). You may pay other fees, such as brokerage commissions and other fees to financial intermediaries which are not reflected in the tables and examples below.
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Shareholder Fees Caption [Text] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Shareholder Fees </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">(fees paid directly from your investment)</span>
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Operating Expenses Caption [Text] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Annual Fund Operating Expenses </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">(expenses that you pay each year as a percentage of the value of your investment)</span>
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Fee Waiver or Reimbursement over Assets, Date of Termination |
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<span style="font-family:Arial;font-size:9.02pt;">April 30, 2026</span>
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Portfolio Turnover [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Portfolio Turnover:</span>
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Portfolio Turnover [Text Block] |
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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 18% of the average value of its portfolio.
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Portfolio Turnover, Rate |
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18.00%
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Expenses Restated to Reflect Current [Text] |
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<span style="color:#000000;font-family:Arial;font-size:9.02pt;">Other Expenses have been restated to reflect current fees for Class I shares.</span>
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Expense Example [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Example:</span>
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Expense Example Narrative [Text Block] |
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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell or hold all of your Fund Shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The calculation of costs for the one-year period takes into account the effect of any current contractual fee waivers and/or reimbursements; and the calculation of costs for the remaining periods takes such fee waivers and/or reimbursements into account only for the first year of each such period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
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Strategy [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Principal Investment Strategies</span>
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Strategy Narrative [Text Block] |
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SSGA Funds Management, Inc. (“SSGA FM” or the “Adviser”), the investment adviser to the Fund, manages the Target Retirement 2025 Fund using a proprietary asset allocation strategy. The Fund is a “fund of funds” that invests in a combination of mutual funds and ETFs sponsored by the Adviser or its affiliates (the “Underlying Funds”). The Underlying Funds may invest in a wide variety of asset classes, including equity and fixed-income securities of issuers anywhere in the world, including emerging markets investments, and including, among others, high yield, commodity, and real estate investments. The Underlying Funds may invest in obligations of domestic U.S. issuers, non-U.S. issuers, or both. The Fund is intended for investors expecting to retire around the year 2025 and who are likely to stop making new investments in the Fund at that time. The Fund is designed for an investor who plans to withdraw the value of the investor's account gradually following that date. The Adviser seeks to optimize the Fund's “glide path” for the wealth accumulation, wealth preservation, and income generation phases of retirement planning and includes adjustments in the critical years immediately preceding and following the retirement date. For example, a Fund with a target retirement date far into the future will typically invest a greater portion of its assets in asset classes with higher risk profiles and the potential for higher returns. As the target date for a Fund approaches, the Adviser will adjust the asset allocation and risk profile of the Fund – its glide path – to what is generally seen to be a more conservative approach to reduce (but not to eliminate) risk by increasing the allocation to asset classes that have historically been subject to lower levels of volatility. A fund intended for investors who have already achieved retirement age would typically invest a greater portion of its assets in bonds and cash items, with a relatively smaller allocation to equity securities. The Underlying Funds employ a wide array of investment styles. For example, the Underlying Funds can buy and sell common stocks of companies of any size, corporate bonds of varying credit quality, U.S. government and agency bonds, mortgage- and asset-backed securities, commodities, real estate and money market instruments. They may hold U.S. or non-U.S. investments. The Underlying Funds may use derivative instruments of any kind, including futures contracts, forward currency contracts, credit default swaps, interest rate swaps and commodities-related derivatives. Derivatives may be used by an Underlying Fund for hedging or risk management purposes, as a substitute for direct investment, or otherwise to seek to enhance the Underlying Fund's total return. The glide path depicted in the chart below shows how the Fund's strategic target allocations among asset classes are expected generally to place more emphasis on fixed income investments and less on equity investments as the target retirement date approaches. The glide path shows the Fund's long term strategic target allocations. The Fund's actual allocations may differ. The Adviser periodically reviews the Fund's target asset allocations and may, at any time, in its discretion, change the target asset allocations or deviate from the target asset allocations when it believes doing so is appropriate to pursue the Fund's investment objective. The glide path is presented only as an illustration of how the process of re-allocation occurs as the Fund approaches its target date.The following table shows the Fund's strategic target allocations to the Underlying Funds as of the date of this Prospectus.Underlying FundsTargetRetirement2025 FundState Street Equity 500 Index II Portfolio20.80State Street Small/Mid Cap Equity Index Portfolio2.73State Street Global All Cap Equity ex-U.S. Index Portfolio14.85State Street Aggregate Bond Index Portfolio20.75SPDR Bloomberg 1-10 Year TIPS ETF18.00SPDR Bloomberg High Yield Bond ETF7.00SPDR Dow Jones Global Real Estate ETF5.00SPDR Portfolio Long Term Treasury ETF0.00SDPR Portfolio Intermediate Term Treasury ETF0.00SPDR Portfolio Short Term Treasury ETF5.90SPDR Portfolio Short Term Corporate Bond ETF1.47SDPR Bloomberg Enhanced Roll Yield Commodity Strategy No K-1 ETF3.50The Fund's actual allocations are expected to differ over time. The Adviser periodically reviews the Fund's target allocations to underlying investment options and may, at any time, in its discretion, change the target allocations or deviate from the target allocations when it believes doing so is appropriate to pursue the Fund's investment objective. The Adviser may modify the selection of Underlying Funds from time to time, and may invest in other Underlying Funds, including any Underlying Funds that may be created in the future. The table is presented for illustrative purposes only. More current information regarding the Fund's allocations may be available on its website: www.ssga.com.
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Risk [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Principal Risks</span>
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Bar Chart and Performance Table [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Performance</span>
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Performance Narrative [Text Block] |
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The bar chart and table below provide some indication of the risks of investing in the Fund by illustrating the variability of the Fund's returns from year-to-year and by showing how the Fund's average annual returns for the periods indicated compared with those of a broad measure of market performance and those of a composite of accounts with similar investment objectives (the “Composite Index”). The Composite Index is a custom composite which comprises each index tracked by the Underlying Funds of the Fund. The S&P 500 Index is a well-known stock market index that includes common stocks of 500 companies from a number of sectors and that measures the performance of the large-cap sector of the market.The bar chart shows how the Class I shares' returns have varied for each full calendar year shown. The Fund's past performance does not necessarily indicate how the Fund will perform in the future.Current performance information for the Fund is available toll free by calling (800) 997-7327 or by visiting our website at www.ssga.com.
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Performance Information Illustrates Variability of Returns [Text] |
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<span style="font-family:Arial;font-size:10.02pt;margin-left:0%;">The bar chart and table below provide some indication of the risks of investing in the Fund by illustrating the variability of the Fund's returns from year-to-year and by showing how the Fund's average annual returns for the periods indicated compared with those of a broad measure of market performance and those of a composite of accounts with similar investment objectives (the </span><span style="font-family:Arial;font-size:10.02pt;">“Composite Index”). The </span><span style="font-family:Arial;font-size:10.02pt;margin-left:0%;">Composite Index is a custom composite which comprises each index tracked by the Underlying Funds of the Fund. The S&P 500 Index is a well-known stock market index that includes common stocks of 500 companies from a number of sectors and that measures the performance of the large-cap sector of the market.</span>
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Performance Availability Phone [Text] |
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<span style="font-family:Arial;font-size:10.02pt;">(800) 997-7327</span>
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Performance Availability Website Address [Text] |
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<span style="font-family:Arial;font-size:10.02pt;">www.ssga.com</span>
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Performance Past Does Not Indicate Future [Text] |
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<span style="font-family:Arial;font-size:10.02pt;">The Fund's past performance does not necessarily</span><span style="font-family:Arial;font-size:10.02pt;margin-left:0%;"> indicate how the Fund will perform in the future.</span>
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Bar Chart [Heading] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Annual Total Returns </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">(years ended 12/31)</span>
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Bar Chart Closing [Text Block] |
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ReturnsQuarter/YearHighest Quarterly Return13.51%Q2 2020Lowest Quarterly Return-12.49%Q1 2020
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Performance Table Heading |
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<span style="font-family:Arial;font-size:10.02pt;font-weight:bold;">Average Annual Total Returns </span><span style="font-family:Arial;font-size:10.02pt;">(for periods ended 12/31/24)</span>
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Performance Table Does Reflect Sales Loads |
rr_PerformanceTableDoesReflectSalesLoads |
<span style="color:#000000;font-family:Arial;font-size:10.02pt;">Except for differences in returns resulting from differences in fees, expenses, </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;margin-left:0%;">and sales charges (as applicable), all share classes would have substantially similar returns because all share classes </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">invest in the same portfolio of securities.</span>
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Performance Table Uses Highest Federal Rate |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;margin-left:0%;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. </span>
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Performance Table Not Relevant to Tax Deferred |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;">After-tax returns depend on an investor's tax situation and may differ from those </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;margin-left:0%;">shown, and after-tax returns are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (</span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">“IRAs”).</span>
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Performance Table One Class of after Tax Shown [Text] |
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<span style="color:#000000;font-family:Arial;font-size:10.02pt;">After tax returns are only shown for Class I and after tax </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;margin-left:0%;">returns will vary for other share classes.</span>
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Performance Table Narrative |
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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns depend on an investor's tax situation and may differ from those shown, and after-tax returns are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).After tax returns are only shown for Class I and after tax returns will vary for other share classes.Except for differences in returns resulting from differences in fees, expenses, and sales charges (as applicable), all share classes would have substantially similar returns because all share classes invest in the same portfolio of securities.
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State Street Target Retirement 2025 Fund | Risk Lose Money [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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You could lose money by investing in the Fund.
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State Street Target Retirement 2025 Fund | Risk Not Insured Depository Institution [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Asset Allocation Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Asset Allocation Risk: The Fund's investment performance depends upon the successful allocation by the Adviser of the Fund's assets among asset classes, geographical regions, industry sectors, and specific issuers and investments. There is no guarantee that the Adviser's allocation techniques and decisions will produce the desired results.
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State Street Target Retirement 2025 Fund | Risk of Investment in Other Pools [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Risk of Investment in Other Pools: When the Fund invests in another pooled investment vehicle, 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.
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State Street Target Retirement 2025 Fund | Target Date Assumption Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Target Date Assumptions Risk: This is the risk that assumptions and forecasts used by the Adviser in developing the Fund's asset allocation glide path are not in line with actual future investment returns and participant savings activities, which could result in losses near, at, or after the target date year or could result in the Fund not providing adequate income at and through retirement.
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State Street Target Retirement 2025 Fund | Longevity Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Longevity Risk: This is the risk that you will outlive your retirement assets.
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State Street Target Retirement 2025 Fund | Below Investment Grade Securities Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Commodities Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Commodities Risk: Commodity prices can have significant volatility, and exposure to commodities can cause the net asset value (“NAV”) of Fund Shares to decline or fluctuate in a rapid and unpredictable manner. A liquid secondary market may not exist for certain commodity investments, which may make it difficult for the Fund to sell them at a desirable price or at the price at which it is carrying them.
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State Street Target Retirement 2025 Fund | Counterparty Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Currency Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Debt Securities Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Depositary Receipts Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Depositary Receipts Risk: Investments in depositary receipts may be less liquid and more volatile than the underlying securities in their primary trading market. If a depositary receipt is denominated in a different currency than its underlying securities, the Fund will be subject to the currency risk of both the investment in the depositary receipt and the underlying security. Holders of depositary receipts may have limited or no rights to take action with respect to the underlying securities or to compel the issuer of the receipts to take action. The prices of depositary receipts may differ from the prices of securities upon which they are based. To the extent the Fund invests in depositary receipts based on securities included in the Index, such differences in prices may increase index tracking risk.
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State Street Target Retirement 2025 Fund | Derivatives Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Emerging Markets Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Equity Investing Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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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.
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State Street Target Retirement 2025 Fund | Geographic Focus Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Geographic Focus Risk: The performance of a fund that invests significantly in one or more countries or geographic regions will be closely tied to market, currency, economic, political, environmental, or regulatory conditions and developments in the countries or regions in which the fund invests, and may be more volatile than the performance of a fund that does not invest significantly in such countries or regions.
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State Street Target Retirement 2025 Fund | Income Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Income Risk: The Fund's income may decline due to falling interest rates or other factors. Issuers of securities held by the Fund may call or redeem the securities during periods of falling interest rates, and the Fund would likely be required to reinvest in securities paying lower interest rates. If an obligation held by the Fund is prepaid, the Fund may have to reinvest the prepayment in other obligations paying income at lower rates.
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State Street Target Retirement 2025 Fund | Indexing Strategy Index Tracking Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Indexing Strategy/Index Tracking Risk: The Fund is managed with an indexing investment strategy, attempting to track the performance of an unmanaged index of securities, regardless of the current or projected performance of the Index or of the actual securities comprising the Index. This differs from an actively-managed fund, which typically seeks to outperform a benchmark index. As a result, the Fund's performance may be less favorable than that of a portfolio managed using an active investment strategy. The structure and composition of the Index will affect the performance, volatility, and risk of the Index and, consequently, the performance, volatility, and risk of the Fund. While the Adviser seeks to track the performance of the Index (i.e., achieve a high degree of correlation with the Index), the Fund's return may not match the return of the Index. The Fund incurs a number of operating expenses not applicable to the Index, and incurs costs in buying and selling securities. In addition, the Fund may not be fully invested at times, generally as a result of cash flows into or out of the Fund or reserves of cash held by the Fund to meet redemptions. The Adviser may attempt to replicate the Index return by investing in fewer than all of the securities in the Index, or in some securities not included in the Index, potentially increasing the risk of divergence between the Fund's return and that of the Index.
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State Street Target Retirement 2025 Fund | Inflation Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
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Inflation Risk: Inflation risk is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the values of a fund's assets can decline. Inflation rates may change frequently and drastically as a result of various factors and the Fund's investments may not keep pace with inflation, which may result in losses to Fund investors or adversely affect the real value of shareholders' investments in the Fund. As such, fixed income securities markets may experience heightened levels of interest rate volatility and liquidity risk.
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State Street Target Retirement 2025 Fund | Inflation Indexed Securities Risk [Member] |
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Risk Return Abstract |
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Risk [Text Block] |
rr_RiskTextBlock |
Inflation-Indexed Securities Risk: The principal amount of an inflation-indexed security typically increases with inflation and decreases with deflation, as measured by a specified index. It is possible that, in a period of declining inflation rates, the Fund could receive at maturity less than the initial principal amount of an inflation-indexed security. Changes in the values of inflation-indexed securities may be difficult to predict, and it is possible that an investment in such securities will have an effect different from that anticipated by the Adviser.
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|
State Street Target Retirement 2025 Fund | IPO Risk [Member] |
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|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
IPO Risk: The Fund may at times have the opportunity to invest in securities offered in initial public offerings (“IPOs”). IPOs involve companies that have no public operating history and therefore entail more risk than established public companies. The prices of securities offered in IPOs can have significant volatility and the Fund may lose money on an investment in such securities. IPO investments in which other clients of the Adviser invest may not be made available to the Fund.
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|
State Street Target Retirement 2025 Fund | Large Capitalization Securities Risk [Member] |
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|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
Large-Capitalization Securities Risk: Returns on investments in securities of large companies could trail the returns on investments in securities of smaller and mid-sized companies. Larger companies may be unable to respond as quickly as smaller and mid-sized companies to competitive challenges or to changes in business, product, financial, or other market conditions. Larger companies may not be able to maintain growth at the high rates that may be achieved by well-managed smaller and mid-sized companies.
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State Street Target Retirement 2025 Fund | Large Transactions Risk [Member] |
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|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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.
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|
State Street Target Retirement 2025 Fund | Liquidity Risk [Member] |
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Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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.
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State Street Target Retirement 2025 Fund | Management Risk [Member] |
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|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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 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.
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State Street Target Retirement 2025 Fund | Market Risk [Member] |
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Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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.
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State Street Target Retirement 2025 Fund | Modeling Risk [Member] |
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Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
Modeling Risk: The Adviser uses quantitative models in an effort to enhance returns and manage risk. Any imperfections, errors or limitations in these models could limit any benefit to the Fund from the use of the models, or could result in incorrect outputs or in investment outcomes different from or opposite to those expected or desired by the Adviser. There can be no assurance that the models will behave as expected in all market conditions. In addition, computer programming used to create quantitative models, or the data on which such models operate, might contain one or more errors.
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State Street Target Retirement 2025 Fund | Mortgage Related and Other Asset Backed Securities Risk [Member] |
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Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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.
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|
State Street Target Retirement 2025 Fund | Non U S Securities Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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.
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|
State Street Target Retirement 2025 Fund | Real Estate Sector Risk [Member] |
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|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
Real Estate Sector Risk: An investment in a real property company may be subject to risks similar to those associated with direct ownership of real estate, including, by way of example, the possibility of declines in the value of real estate, losses from casualty or condemnation, and changes in local and general economic conditions, supply and demand, interest rates, environmental liability, zoning laws, regulatory limitations on rents, property taxes, and operating expenses. Some real property companies have limited diversification because they invest in a limited number of properties, a narrow geographic area, or a single type of property.
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|
State Street Target Retirement 2025 Fund | REIT Risk [Member] |
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|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
REIT Risk: Real estate investment trusts (“REITs”) are subject to the risks associated with investing in the securities of real property companies. In particular, REITs may be affected by changes in the values of the underlying properties that they own or operate. Further, REITs are dependent upon specialized management skills, and their investments may be concentrated in relatively few properties, or in a small geographic area or a single property type. REITs are also subject to heavy cash flow dependency and, as a result, are particularly reliant on the proper functioning of capital markets. A variety of economic and other factors may adversely affect a lessee's ability to meet its obligations to a REIT. In the event of a default by a lessee, the REIT may experience delays in enforcing its rights as a lessor and may incur substantial costs associated in protecting its investments. In addition, a REIT could fail to qualify for favorable regulatory treatment.
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|
State Street Target Retirement 2025 Fund | Restricted Securities Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
Restricted Securities Risk: The Fund may hold securities that have not been registered for sale to the public under the U.S. federal securities laws. There can be no assurance that a trading market will exist at any time for any particular restricted security. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Fund from disposing of them promptly at reasonable prices. The Fund may have to bear the expense of registering the securities for resale and the risk of substantial delays in effecting the registration. Also, restricted securities may be difficult to value because market quotations may not be readily available, and the securities may have significant volatility.
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|
State Street Target Retirement 2025 Fund | Small Mid and Micro Capitalization Securities Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
Small-, Mid- and Micro-Capitalization Securities Risk: The securities of small-, mid- and micro-capitalization companies may be more volatile and may involve more risk than the securities of larger companies. These companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, and may depend on a few key employees. In addition, these companies may have been recently organized and may have little or no track record of success. The securities of smaller companies may trade less frequently and in smaller volumes than more widely held securities. Some securities of smaller issuers may be illiquid or may be restricted as to resale, and their values may have significant volatility. 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. Returns on investments in securities of small-, mid- and micro-capitalization companies could trail the returns on investments in securities of larger companies.
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|
State Street Target Retirement 2025 Fund | Unconstrained Sector Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
Unconstrained Sector Risk: The Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. Greater investment focus on one or more sectors or industries increases the potential for volatility and the risk that events negatively affecting such sectors or industries could reduce returns, potentially causing the value of the Fund's Shares to decrease, perhaps significantly.
|
|
State Street Target Retirement 2025 Fund | US Government Securities Risk [Member] |
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|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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 Congres sional 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.
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|
State Street Target Retirement 2025 Fund | US Treasury Obligations Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
U.S. Treasury Obligations Risk: U.S. Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the U.S. government may cause the value of the Fund's U.S. Treasury obligations to decline.
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|
State Street Target Retirement 2025 Fund | Valuation Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
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.
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|
State Street Target Retirement 2025 Fund | When Issued TBA and Delayed Delivery Securities Risk [Member] |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Risk [Text Block] |
rr_RiskTextBlock |
When-Issued, TBA and Delayed Delivery Securities Risk: The Fund may purchase securities on a when-issued, to-be-announced (“TBA”) or delayed delivery basis and may purchase securities on a forward commitment basis. The purchase price of the securities is typically fixed at the time of the commitment, but delivery and payment can take place a month or more after the date of the commitment. At the time of delivery of the securities, the value may be more or less than the purchase or sale price. Purchase of securities on a when-issued, TBA, delayed delivery, or forward commitment basis may give rise to investment leverage, and may result in increased volatility of the Fund's NAV. Default by, or bankruptcy of, a counterparty to a when-issued, TBA or delayed delivery transaction would expose the Fund to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools specified in such transaction. The Financial Industry Regulatory Authority, Inc. (“FINRA”) imposes mandatory margin requirements for certain types of when-issued, delayed delivery or forward commitment transactions (including TBA transactions), with limited exceptions. Such transactions require mandatory collateralization which may increase the cost of such transactions and impose added operational complexity.
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|
State Street Target Retirement 2025 Fund | Class I |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) |
rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice |
none
|
|
Maximum Deferred Sales Charge (Load) (as a percentage of the lower of the sale proceeds or the original offering price) |
rr_MaximumDeferredSalesChargeOverOther |
none
|
|
Management Fee |
rr_ManagementFeesOverAssets |
0.05%
|
|
Distribution and/or Shareholder Service (12b-1) Fees |
rr_DistributionAndService12b1FeesOverAssets |
none
|
|
Other Expenses |
rr_OtherExpensesOverAssets |
0.27%
|
[1] |
Acquired Fund Fees and Expenses |
rr_AcquiredFundFeesAndExpensesOverAssets |
0.10%
|
|
Total Annual Fund Operating Expenses |
rr_ExpensesOverAssets |
0.42%
|
|
Less Fee Waivers and/or Expense Reimbursements |
rr_FeeWaiverOrReimbursementOverAssets |
(0.13%)
|
[2] |
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements |
rr_NetExpensesOverAssets |
0.29%
|
|
1 year |
rr_ExpenseExampleYear01 |
$ 30
|
|
3 years |
rr_ExpenseExampleYear03 |
122
|
|
5 years |
rr_ExpenseExampleYear05 |
222
|
|
10 years |
rr_ExpenseExampleYear10 |
$ 517
|
|
2015 |
rr_AnnualReturn2015 |
(1.87%)
|
|
2016 |
rr_AnnualReturn2016 |
8.01%
|
|
2017 |
rr_AnnualReturn2017 |
16.54%
|
|
2018 |
rr_AnnualReturn2018 |
(5.48%)
|
|
2019 |
rr_AnnualReturn2019 |
20.76%
|
|
2020 |
rr_AnnualReturn2020 |
14.66%
|
|
2021 |
rr_AnnualReturn2021 |
10.03%
|
|
2022 |
rr_AnnualReturn2022 |
(15.47%)
|
|
2023 |
rr_AnnualReturn2023 |
13.58%
|
|
2024 |
rr_AnnualReturn2024 |
8.76%
|
|
Highest Quarterly Return, Label |
rr_HighestQuarterlyReturnLabel |
<span style="font-family:Arial;font-size:9.02pt;font-weight:bold;margin-left:0.0pt;">Highest Quarterly Return</span>
|
|
Highest Quarterly Return, Date |
rr_BarChartHighestQuarterlyReturnDate |
Jun. 30, 2020
|
|
Highest Quarterly Return |
rr_BarChartHighestQuarterlyReturn |
13.51%
|
|
Lowest Quarterly Return, Label |
rr_LowestQuarterlyReturnLabel |
<span style="font-family:Arial;font-size:9.02pt;font-weight:bold;margin-left:0.0pt;">Lowest Quarterly Return</span>
|
|
Lowest Quarterly Return, Date |
rr_BarChartLowestQuarterlyReturnDate |
Mar. 31, 2020
|
|
Lowest Quarterly Return |
rr_BarChartLowestQuarterlyReturn |
(12.49%)
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
8.76%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
5.67%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
6.39%
|
|
State Street Target Retirement 2025 Fund | Class K |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) |
rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice |
none
|
|
Maximum Deferred Sales Charge (Load) (as a percentage of the lower of the sale proceeds or the original offering price) |
rr_MaximumDeferredSalesChargeOverOther |
none
|
|
Management Fee |
rr_ManagementFeesOverAssets |
0.05%
|
|
Distribution and/or Shareholder Service (12b-1) Fees |
rr_DistributionAndService12b1FeesOverAssets |
none
|
|
Other Expenses |
rr_OtherExpensesOverAssets |
0.07%
|
[1] |
Acquired Fund Fees and Expenses |
rr_AcquiredFundFeesAndExpensesOverAssets |
0.10%
|
|
Total Annual Fund Operating Expenses |
rr_ExpensesOverAssets |
0.22%
|
|
Less Fee Waivers and/or Expense Reimbursements |
rr_FeeWaiverOrReimbursementOverAssets |
(0.13%)
|
[2] |
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements |
rr_NetExpensesOverAssets |
0.09%
|
|
1 year |
rr_ExpenseExampleYear01 |
$ 9
|
|
3 years |
rr_ExpenseExampleYear03 |
58
|
|
5 years |
rr_ExpenseExampleYear05 |
111
|
|
10 years |
rr_ExpenseExampleYear10 |
$ 267
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
8.92%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
5.93%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
6.53%
|
|
State Street Target Retirement 2025 Fund | Class R3 |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) |
rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice |
none
|
|
Maximum Deferred Sales Charge (Load) (as a percentage of the lower of the sale proceeds or the original offering price) |
rr_MaximumDeferredSalesChargeOverOther |
none
|
|
Management Fee |
rr_ManagementFeesOverAssets |
0.05%
|
|
Distribution and/or Shareholder Service (12b-1) Fees |
rr_DistributionAndService12b1FeesOverAssets |
0.25%
|
|
Other Expenses |
rr_OtherExpensesOverAssets |
0.32%
|
[1] |
Acquired Fund Fees and Expenses |
rr_AcquiredFundFeesAndExpensesOverAssets |
0.10%
|
|
Total Annual Fund Operating Expenses |
rr_ExpensesOverAssets |
0.72%
|
|
Less Fee Waivers and/or Expense Reimbursements |
rr_FeeWaiverOrReimbursementOverAssets |
(0.13%)
|
[2] |
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements |
rr_NetExpensesOverAssets |
0.59%
|
|
1 year |
rr_ExpenseExampleYear01 |
$ 60
|
|
3 years |
rr_ExpenseExampleYear03 |
217
|
|
5 years |
rr_ExpenseExampleYear05 |
388
|
|
10 years |
rr_ExpenseExampleYear10 |
$ 882
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
8.27%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
5.40%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
6.00%
|
|
State Street Target Retirement 2025 Fund | Return After Taxes on Distributions | Class I |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
6.56%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
3.86%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
4.86%
|
|
State Street Target Retirement 2025 Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class I |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
5.76%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
3.91%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
4.59%
|
|
State Street Target Retirement 2025 Fund | S&P 500 Index (reflects no deduction for fees, expenses or taxes) |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
25.02%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
14.53%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
13.10%
|
|
State Street Target Retirement 2025 Fund | State Street Target Retirement 2025 Composite Index (reflects no deduction for fees, expenses or taxes) |
|
|
|
Risk Return Abstract |
rr_RiskReturnAbstract |
|
|
OneYear |
rr_AverageAnnualReturnYear01 |
8.84%
|
|
FiveYears |
rr_AverageAnnualReturnYear05 |
5.96%
|
|
TenYears |
rr_AverageAnnualReturnYear10 |
6.61%
|
|
|
|