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FlexShares Morningstar Emerging Markets Factor Tilt Index Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FlexShares® Morningstar Emerging Markets Factor Tilt Index Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Morningstar® Emerging Markets Factor Tilt IndexSM (the “Underlying Index”).
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination March 1, 2023
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock 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. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 40% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 40.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your 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 (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, possess greater exposure to size and value factors relative to the Morningstar Emerging Markets Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of companies incorporated in emerging-market countries. The Underlying Index seeks to achieve increased exposures to size and value factors, or a “factor tilt”, by adjusting the Parent Index’s constituent weights to achieve a slightly greater weight on companies with smaller market capitalizations or lower valuations, as determined by Morningstar, Inc. (the “Index Provider”), pursuant to its index methodology. The Underlying Index is designed to include companies with enhanced risk-return characteristics relative to the broader emerging equity market by featuring size and value risk premiums, which Northern Trust Investments, Inc. (“NTI” or “Investment Adviser”) believes have been historically demonstrated over a full market cycle. As of December 31, 2021, the Underlying Index was comprised of 3,400 issues with market capitalizations ranging from $1.7 billion to $392.3 billion. The Underlying Index is governed by published, objective rules for security selection, 
exclusion, rebalancing and adjustments for corporate actions and is reconstituted on a semi-annual basis and is rebalanced quarterly. The Fund generally reconstitutes and rebalances its portfolio in accordance with the Underlying Index. 
NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. 
NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. 
Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. 
The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. 
The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). 
From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more 
particular countries or geographic regions. As of December 31, 2021, the Fund focused its investments in China, Taiwan and South Korea. 
Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. 
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. 
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments. The Fund is subject to certain risks, including the principal risks noted below, any of which may adversely affect the Fund’s net asset value (“NAV”), trading price, yield, total return and ability to meet its investment objective. Each risk noted below is considered a principal risk of investing in the Fund, regardless of the order in which it appears. The significance of each risk factor below may change over time and you should review each risk factor carefully.
Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.
Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.
 
Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than compa- 
nies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information. 
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. 
Geographic Risk is the risk that if a fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an economic, business or political development affecting that country or region may affect the value of the fund’s investments more than if the fund’s investments were not so concentrated in such country or region. 
• China Investment Risk is the risk associated with investments in companies located or operating in China, such as nationalization, expropriation, or confiscation of property; alteration or discontinuation of economic reforms; and considerable degrees of economic, political and social instability. Investors in Chinese markets generally experience difficulties in obtaining information necessary for investigations into and/or litigation against Chinese companies, as well as in obtaining and/or enforcing judgements due to a lack of publicly available information; and there are generally limited legal remedies for shareholders. Internal social unrest or confrontations with other neighboring countries, including military conflicts, may disrupt economic development in China and result in a greater risk of currency fluctuations, currency convertibility, interest rate fluctuations and higher rates of inflation. Export growth continues to be a major driver of China’s rapid economic growth. As a result, a reduction in spending on Chinese products and services, the institution of additional tariffs or other trade barriers, including as a result of heightened trade tensions between China and the U.S., or a downturn in any of the economies of China’s key trading partners may have an adverse impact on the Chinese economy. The inability of the Public Company Accounting Oversight Board (“PCAOB”) to inspect audit work papers and practices of PCAOB-registered accounting firms in China with respect to their audit work of U.S. reporting companies may impose significant additional risks associated with investments in China. Certain securities issued by companies located or operating in China, such as China 
  A-shares, are subject to trading restrictions and suspensions, quota limitations and sudden changes in those limitations, and operational, clearing and settlement risks.
• Taiwan Investment Risk is the risk of investing in securities of Taiwanese issuers. Specifically, Taiwan’s geographic proximity and history of political contention with China have resulted in ongoing tensions between the two countries, which may materially affect the Taiwanese economy and its securities market. Investments in securities of Taiwanese companies are subject to Taiwan’s heavy dependence on exports. Reductions in spending on Taiwanese products and services, labor shortages, institution of tariffs or other trade barriers, or a downturn in any of the economies of Taiwan’s key trading partners, including the United States, may have an adverse impact on the Taiwanese economy and the values of Taiwanese companies.
• South Korea Investment Risk is the risk that South Korean issuers in which the Fund invests may subject the Fund to legal, regulatory, political, currency, security, and economic risks that are specific to South Korea. In addition, economic and political developments of South Korea’s neighbors, including escalated tensions involving North Korea and any outbreak of hostilities involving North Korea, or even the threat of an outbreak of hostilities, may have a severe adverse effect on the South Korean economy. 
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. 
Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally 
subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts. 
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, 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 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 and could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. An outbreak of COVID-19, a respiratory disease caused by a novel coronavirus, has negatively affected the worldwide economy, the financial health of individual companies and the market in significant and unforeseen ways. The future impact of COVID-19 is currently unknown. The effects to public health, business and market conditions resulting from the COVID-19 pandemic may have a significant negative impact on the performance of the Fund’s investments. 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. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track its Underlying Index or cause delays in the Underlying Index’s rebalancing or reconstitution 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. Because the Fund is designed to maintain a high level of exposure to its Underlying Index at all times, it will not take any steps to invest defensively or otherwise reduce the risk of loss during market downturns. 
Market risk includes the risk that a particular style of investing, such as growth or value, may underperform the market generally. The market value of the securities in which the Fund invests may go up or down in response to the prospects of individual companies, particular sectors or governments and/or general economic conditions throughout the world due to increasingly interconnected global economies and financial markets. As a result, whether or not the Fund invests in securities of issuers located in or with significant exposure to the countries directly affected, the value and liquidity of the Fund’s investments may be negatively affected. Securities markets may experience great short-term volatility and may fall sharply at times. Different markets may behave differently from each other and a foreign market may move in the opposite direction from the U.S. market. 
Price changes may be temporary or last for extended periods. You could lose money over short periods due to fluctuation in the market prices of the Fund’s shares in response to market movements, and over longer periods during market downturns. 
Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added or removed, respectively, from 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 an 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 is the risk that the Fund’s performance may vary substantially from the performance of the Underlying Index. The Fund’s performance may vary from the performance of the Underlying Index for a number of reasons including that the Fund incurs operating expenses that the Underlying Index does not and that the Fund 
accepts custom baskets. Tracking error risk may be higher for funds that track a foreign index, or an index that includes foreign securities, because regulatory and reporting requirements may differ from those in the U.S., and there is a heightened risk associated with limited availability and reliability of data used to construct the index. 
Sampling Risk is the risk that the Fund’s use of a representative sampling approach may 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. 
Value Investing Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated. 
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. This risk may be heightened because of its investments in non-U.S. securities. 
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 Index guaranteed. A security included in an 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. Unusual market conditions may cause the provider of the Underlying Index to postpone a scheduled rebalance, which could cause the Underlying Index to vary from its normal or expected composition. 
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. 
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.
• Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. 
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 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. 
It is possible to lose money on an investment in the Fund. 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. 
Risk Lose Money [Text] rr_RiskLoseMoney It is possible to lose money on an investment in the Fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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. 
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund. Past performance (before and after taxes) does not necessarily indicate how
the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com. 
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress flexshares.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) does not necessarily indicate howthe Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the periods in the bar chart above:
Best Quarter (12/31/2020): 22.97%
Worst Quarter (3/31/2020): -27.43%
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2021)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes Reflects no deduction for fees, expenses or taxes.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
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. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.
FlexShares Morningstar Emerging Markets Factor Tilt Index Fund | FlexShares Morningstar Emerging Markets Factor Tilt Index Fund  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.59%
Distribution (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.01%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.60%
Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.01%) [1]
Total Annual Fund Operating Expenses After Expense Reimbursement rr_NetExpensesOverAssets 0.59%
1 Year rr_ExpenseExampleYear01 $ 60
3 Years rr_ExpenseExampleYear03 191
5 Years rr_ExpenseExampleYear05 334
10 Years rr_ExpenseExampleYear10 $ 749
2013 rr_AnnualReturn2013 (2.55%)
2014 rr_AnnualReturn2014 (2.13%)
2015 rr_AnnualReturn2015 (12.97%)
2016 rr_AnnualReturn2016 12.05%
2017 rr_AnnualReturn2017 32.37%
2018 rr_AnnualReturn2018 (16.14%)
2019 rr_AnnualReturn2019 14.17%
2020 rr_AnnualReturn2020 11.44%
2021 rr_AnnualReturn2021 5.39%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 22.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.43%)
One Year rr_AverageAnnualReturnYear01 5.39%
Five Year rr_AverageAnnualReturnYear05 8.28%
Since Inception of Fund rr_AverageAnnualReturnSinceInception 4.21%
Inception Date of Fund rr_AverageAnnualReturnInceptionDate Sep. 25, 2012
FlexShares Morningstar Emerging Markets Factor Tilt Index Fund | After Taxes on Distributions | FlexShares Morningstar Emerging Markets Factor Tilt Index Fund  
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 4.61%
Five Year rr_AverageAnnualReturnYear05 7.64%
Since Inception of Fund rr_AverageAnnualReturnSinceInception 3.70%
FlexShares Morningstar Emerging Markets Factor Tilt Index Fund | After Taxes on Distributions and Sale of Shares | FlexShares Morningstar Emerging Markets Factor Tilt Index Fund  
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 3.75%
Five Year rr_AverageAnnualReturnYear05 6.51%
Since Inception of Fund rr_AverageAnnualReturnSinceInception 3.28%
FlexShares Morningstar Emerging Markets Factor Tilt Index Fund | Morningstar® Emerging Markets Factor Tilt Index℠  
Risk/Return: rr_RiskReturnAbstract  
One Year rr_AverageAnnualReturnYear01 6.42% [2]
Five Year rr_AverageAnnualReturnYear05 9.12% [2]
Since Inception of Fund rr_AverageAnnualReturnSinceInception 4.96% [2]
[1] Northern Trust Investments, Inc. (“NTI” or the “Investment Adviser”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.59%. This contractual limitation may not be terminated before March 1, 2023 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders.
[2] Reflects no deduction for fees, expenses or taxes.