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S000062125 [Member] Investment Risks - FlexShares High Yield Value-Scored Bond Index Fund
Oct. 31, 2025
Income Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.
Market Risks [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, elevated levels of government debt, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions
caused by local or regional events such as financial institution failures, changes in trade regulation or economic sanctions, internal unrest and discord, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.
Index Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.
Tracking Error Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.
Sampling Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in
the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.
Authorized Participant Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.
Calculation Methodology Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.
Market Trading Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.
Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.
Credit or Default Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.
Debt Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.
Derivatives Risks [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.
•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.
Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.
•Industrials Sector Risk is the risk that companies in the industrials sector may be significantly affected by, among other things, worldwide economic growth, supply and demand for specific products and services, rapid technological developments, international political and economic developments, environmental issues, and tax and governmental regulatory policies.
Interest Rate Maturity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.
Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Liquidity Risk is the risk that certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity Risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and/or purchasing and selling such investments, may be unable to achieve a high degree of correlation with the Underlying Index. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the
Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.
Foreign Issuer Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.
Prepayment or Call Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.
TBA Transactions Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA trans
actions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.
Securities Lending Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.
Valuation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.
High Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
High Portfolio Turnover Risk is the risk that active and frequent trading of the Fund’s portfolio securities may
result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs, which could reduce the Fund’s return.
Distressed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Distressed Securities Risk is the substantial risk of investing in distressed securities that is in addition to the risks of investing in non-investment grade securities generally. NTI defines securities issued by companies whose financial condition is troubled or uncertain and that may be involved in bankruptcy proceedings, reorganizations or financial restructurings as “distressed securities.” Distressed securities are speculative and involve a substantial risk that principal will not be paid. In addition, the Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. These securities may present a substantial risk of default. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.
Substantial Volatility Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Substantial Volatility Risk is the risk that the value of the securities in the Fund’s portfolio may fluctuate, sometimes rapidly and unpredictably at a greater level than the overall market. There is a risk that the Fund could have substantial volatility.
Value Score Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Value Score Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued will not appreciate in value as anticipated. Although the Underlying Index is designed to measure a portfolio of bonds of companies with the potential for higher yields and less risk of insolvency relative to the Parent Index, there is no assurance that the Underlying Index or Fund will be comprised of such securities. Accordingly, the Fund may be subject to greater credit risk, price volatility and risk of loss relative to the Parent Index.
High Yield Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
High Yield Securities Risk is the risk that the Fund will be subject to greater credit risk, price volatility and risk of loss than if it invested primarily in investment grade securities,
which can adversely impact the Fund’s return and NAV. High yield securities are considered highly speculative and are subject to increased risk of an issuer’s inability to make principal and interest payments. The Underlying Index is designed to be comprised of securities with the potential for higher yields as compared to the overall high yield corporate bond market. As such, the Fund is expected to exhibit greater sensitivity to market fluctuations.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] It is possible to lose money on an investment in the Fund.
Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank.