Label | Element | Value | ||
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William Blair Emerging Markets Growth Fund | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk/Return [Heading] | rr_RiskReturnHeading | WILLIAM BLAIR EMERGING MARKETS GROWTH FUND SUMMARY | ||
Objective [Heading] | rr_ObjectiveHeading | INVESTMENT OBJECTIVE: | ||
Objective, Primary [Text Block] | rr_ObjectivePrimaryTextBlock | The William Blair Emerging Markets Growth Fund seeks long-term capital appreciation. | ||
Expense [Heading] | rr_ExpenseHeading | FEES AND EXPENSES: | ||
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. 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. | ||
Shareholder Fees Caption [Text] | rr_ShareholderFeesCaption | Shareholder Fees (fees paid directly from your investment): | ||
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 | April 30, 2026 | ||
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 may indicate higher transaction costs and may result inhigher 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 81% of the average value of its portfolio. | ||
Portfolio Turnover, Rate | rr_PortfolioTurnoverRate | 81.00% | ||
Expense Example [Heading] | rr_ExpenseExampleHeading | Example: | ||
Expense Example Narrative [Text Block] | rr_ExpenseExampleNarrativeTextBlock | This example is intended to help you compare the cost of investing in shares of 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 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 the Fund’s operating expenses remain the same. The figures reflect the expense limitation for the first 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 | Under normal market conditions, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in emerging markets securities. The Fund invests primarily in a diversified portfolio of equity securities, including common stocks and other forms of equity investments (e.g., securities convertible into common stocks), issued by emerging market companies of all sizes that the Adviser believes have above-average growth, profitability and quality characteristics. The Adviser seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development. Emerging market companies, for purposes of the Fund, are companies organized under the laws of an emerging market country or that have securities traded principally on an exchange or over‑the‑counter in an emerging market country. Currently, emerging markets include every country in the world except the United States, Canada, Japan, Australia, New Zealand, Hong Kong, Singapore and most Western European countries. The Fund’s investments are normally allocated among at least six different countries and no more than 50% of the Fund’s equity holdings may be invested in securities of issuers in one country at any given time. In choosing investments, the Adviser performs fundamental company analysis and focuses on stock selection. The Adviser generally seeks equity securities, including common stocks, of emerging market companies that historically have had superior growth, profitability and quality relative to local markets and relative to companies within the same industry worldwide, and that are expected to continue such performance. Such companies generally will exhibit superior business fundamentals, including leadership in their field, quality products or services, distinctive marketing and distribution, pricing flexibility and revenue from products or services consumed on a steady, recurring basis. These business characteristics should be accompanied by management that is shareholder return-oriented and that uses conservative accounting policies. Companies with above-average returns on equity, strong balance sheets and consistent, above-average earnings growth will be the primary focus. Stock selection will take into account both local and global comparisons. The Adviser will vary the Fund’s sector and geographic diversification based upon the Adviser’s ongoing evaluation of economic, market and political trends throughout the world. In making decisions regarding country allocation, the Adviser will consider such factors as the conditions and growth potential of various economies and securities markets, currency exchange rates, technological developments in the various countries and other pertinent financial, social, national and political factors.
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Risk [Heading] | rr_RiskHeading | PRINCIPAL RISKS: | ||
Bar Chart and Performance Table [Heading] | rr_BarChartAndPerformanceTableHeading | FUND PERFORMANCE HISTORY: | ||
Performance Narrative [Text Block] | rr_PerformanceNarrativeTextBlock | The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for the periods indicated compare with those of a broad measure of market performance that is generally representative of the market sectors or types of investments in which the Fund invests. The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. For more recent performance information, go to www.williamblairfunds.com or call 1‑800‑635‑2886. | ||
Performance Information Illustrates Variability of Returns [Text] | rr_PerformanceInformationIllustratesVariabilityOfReturns | The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for the periods indicated compare with those of a broad measure of market performance that is generally representative of the market sectors or types of investments in which the Fund invests. | ||
Performance Availability Phone [Text] | rr_PerformanceAvailabilityPhone | 1‑800‑635‑2886 | ||
Performance Availability Website Address [Text] | rr_PerformanceAvailabilityWebSiteAddress | www.williamblairfunds.com | ||
Performance Past Does Not Indicate Future [Text] | rr_PerformancePastDoesNotIndicateFuture | The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. | ||
Bar Chart [Heading] | rr_BarChartHeading | Annual Total Returns. | ||
Bar Chart Narrative [Text Block] | rr_BarChartNarrativeTextBlock | The bar chart below provides an illustration of how the Fund’s Class N shares performance has varied in each of the last ten calendar years. | ||
Bar Chart Closing [Text Block] | rr_BarChartClosingTextBlock | Highest Quarterly Return30.41% ( )Lowest Quarterly Return(20.85)% ( ) |
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Performance Table Heading | rr_PerformanceTableHeading | Average Annual Total Returns (For the periods ended December 31, 2024). | ||
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 are not relevant to investors who hold their Fund shares through tax‑deferred arrangements, such as 401(k) plans or individual retirement accounts. | ||
Performance Table One Class of after Tax Shown [Text] | rr_PerformanceTableOneClassOfAfterTaxShown | The table below shows returns on a before‑tax and after‑tax basis for Class N shares and on a before‑tax basis for Class I and Class R6 shares. After‑tax returns for Class I and Class R6 shares will vary. | ||
Performance Table Explanation after Tax Higher | rr_PerformanceTableExplanationAfterTaxHigher | In some instances, the “Return After Taxes on Distributions and Sale of Fund Shares” may be greater than the “Return Before Taxes” because the investor is assumed to be able to use the capital loss on the sale of Fund shares to offset other taxable capital gains. | ||
Performance Table Narrative | rr_PerformanceTableNarrativeTextBlock | The table below shows returns on a before‑tax and after‑tax basis for Class N shares and on a before‑tax basis for Class I and Class R6 shares. After‑tax returns for Class I and Class R6 shares will vary. 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. In some instances, the “Return After Taxes on Distributions and Sale of Fund Shares” may be greater than the “Return Before Taxes” because the investor is assumed to be able to use the capital loss on the sale of Fund shares to offset other taxable capital gains. Actual after‑tax returns depend on an investor’s tax situation and may differ from those shown. After‑tax returns are not relevant to investors who hold their Fund shares through tax‑deferred arrangements, such as 401(k) plans or individual retirement accounts. | ||
William Blair Emerging Markets Growth Fund | Risk Lose Money [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | The Fund’s returns will vary, and you could lose money by investing in the Fund. | ||
William Blair Emerging Markets Growth Fund | Equity Funds General Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Equity Funds General Risk. The value of equity securities the Fund holds might decrease in response to the activities of an individual company or in response to general market, business and economic conditions. If this occurs, the Fund’s share price may also decrease. In addition, there is the risk that individual securities may not perform as expected or a strategy used by the Adviser may fail to produce its intended result.
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William Blair Emerging Markets Growth Fund | Market Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Market Risk. The value of the Fund’s investments may go up or down, sometimes rapidly or unpredictably. The value of an investment may decline due to factors affecting securities markets generally or particular industries represented in the securities markets. The value of an investment may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, recessions, inflation, rapid interest rate changes, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Events such as war, geopolitical risk, acts of terrorism, social unrest, tariffs and other restrictions on trade, natural disasters, the spread of infectious illness or other public health threats, or the threat or potential of one or more such events and developments could also significantly impact the Fund and its investments. The value of an investment may also decline due to factors that affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within an industry. During a general downturn in the securities markets, multiple asset classes may decline in value simultaneously. Geopolitical and other events may also disrupt securities markets and adversely affect global economies and markets and thereby decrease the value of the Fund’s investments.
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William Blair Emerging Markets Growth Fund | Foreign Investment Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Foreign Investment Risk. The risks of foreign investments may include less publicly available information, less stringent investor protections and disclosure standards, less governmental regulation and supervision of foreign stock exchanges, brokers and issuers, share registration and custody, a lack of uniform accounting, auditing and financial reporting standards, practices and requirements, the possibility of expropriation, seizure or nationalization, confiscatory taxation, limits on repatriation, adverse changes in investment or exchange control regulations, political instability, restrictions on the flow of international capital, imposition of foreign withholding or other taxes, fluctuating currencies, inflation, difficulty in obtaining and enforcing judgments against foreign entities or other adverse political, social or diplomatic developments that could affect the Fund’s investments. Foreign investments may be less liquid and their prices more volatile than the securities of U.S. companies. The Fund is expected to incur operating expenses that are higher than those of mutual funds investing exclusively in U.S. equity securities due to the higher custodial fees associated with foreign securities investments.
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William Blair Emerging Markets Growth Fund | Share Ownership Concentration Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Share Ownership Concentration Risk. To the extent that a significant portion of the Fund’s shares is held by a limited number of shareholders or their affiliates, there is a risk that the share trading activities of these shareholders could disrupt the Fund’s investment strategies, which could have adverse consequences for the Fund and other shareholders (e.g., by requiring the Fund to sell investments at inopportune times or causing the Fund to maintain larger-than-expected cash positions pending acquisition of investments). In addition, separate accounts managed by the Adviser may invest in the Fund and, therefore, the Adviser at times may have discretionary authority over a significant portion of the assets of the Fund. In such instances, the Adviser’s decision to make changes to or rebalance its clients’ allocations in the separate accounts may substantially impact the Fund’s performance.
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William Blair Emerging Markets Growth Fund | Style Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Style Risk. Different investment styles (e.g., growth vs. value, quality bias, market capitalization focus) tend to shift in and out of favor depending on market conditions and investor sentiment, and at times when the growth investment style used by the Adviser for the Fund is out of favor, the Fund may underperform other equity funds that use different investment styles.
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William Blair Emerging Markets Growth Fund | Operational and Technology Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Operational and Technology Risk. Cyber-attacks, disruptions, or failures that affect the Fund’s service providers, counterparties, market participants, or issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
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William Blair Emerging Markets Growth Fund | Currency Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Currency Risk. The value of the Fund’s portfolio may be affected by changes in exchange rates or control regulations. Currency exchange rates may fluctuate significantly over short periods of time for a number of reasons, including changes in interest rates. If a local currency gains against the U.S. dollar, the value of the security increases in U.S. dollar terms. If a local currency declines against the U.S. dollar, the value of the security decreases in U.S. dollar terms. The currencies of emerging market countries may experience a devaluation relative to the U.S. dollar, and continued devaluations may adversely affect the value of the Fund’s assets denominated in such currencies. Many emerging market countries have experienced substantial rates of inflation for many years, and continued inflation may adversely affect the economies and securities markets of such countries.
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William Blair Emerging Markets Growth Fund | Emerging Markets Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Emerging Markets Risk. Foreign investment risk is typically magnified in emerging markets, which are the less developed and developing nations.
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William Blair Emerging Markets Growth Fund | Geographic Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Geographic Risk. To the extent that the Fund invests a significant portion of its assets in any one country or geographic region, the Fund will be subject to greater risk of loss or volatility than if the Fund always maintained wide geographic diversity among the countries and geographic regions in which it invests. Investing in any one country or geographic region makes the Fund more vulnerable to the risks of adverse securities markets, exchange rates and social, political, regulatory and economic events in that one country or geographic region.
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William Blair Emerging Markets Growth Fund | Smaller Company Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Smaller Company Risk. Stocks of smaller companies involve greater risk than those of larger, more established companies. This is because smaller companies may be in earlier stages of development, may be dependent on a small number of products or services, may lack substantial capital reserves and/or do not have proven track records. Smaller companies may be traded in low volumes. This can increase volatility and increase the risk that the Fund will not be able to sell a security on short notice at a reasonable price. The securities of smaller companies may be more volatile and less liquid than securities of large capitalized companies.
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William Blair Emerging Markets Growth Fund | Liquidity Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Liquidity Risk. Investments that trade less frequently can be more difficult or more costly to buy, or to sell, than more liquid or active investments. It may not be possible to sell or otherwise dispose of illiquid securities both at the price and within a time period deemed desirable by the Fund.
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William Blair Emerging Markets Growth Fund | Focus Risk [Member] | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Risk [Text Block] | rr_RiskTextBlock | Focus Risk. To the extent that the Fund focuses its investments in particular industries, asset classes or sectors of the economy, any market changes affecting companies in those industries, asset classes or sectors may impact the Fund’s performance.
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William Blair Emerging Markets Growth Fund | Class N | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Maximum Sales Charge (Load) Imposed on Purchases | rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice | none | ||
Redemption Fee | rr_RedemptionFeeOverRedemption | none | ||
Management Fee | rr_ManagementFeesOverAssets | 0.94% | ||
Distribution (Rule 12b-1) Fee | rr_DistributionAndService12b1FeesOverAssets | 0.25% | ||
Other Expenses | rr_OtherExpensesOverAssets | 0.24% | ||
Total Annual Fund Operating Expenses | rr_ExpensesOverAssets | 1.43% | ||
Fee Waiver and/or Expense Reimbursement | rr_FeeWaiverOrReimbursementOverAssets | 0.19% | [1] | |
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement | rr_NetExpensesOverAssets | 1.24% | ||
1 Year | rr_ExpenseExampleYear01 | $ 126 | ||
3 Years | rr_ExpenseExampleYear03 | 434 | ||
5 Years | rr_ExpenseExampleYear05 | 764 | ||
10 Years | rr_ExpenseExampleYear10 | $ 1,697 | ||
2015 | rr_AnnualReturn2015 | (15.03%) | ||
2016 | rr_AnnualReturn2016 | 1.49% | ||
2017 | rr_AnnualReturn2017 | 48.53% | ||
2018 | rr_AnnualReturn2018 | (21.61%) | ||
2019 | rr_AnnualReturn2019 | 27.89% | ||
2020 | rr_AnnualReturn2020 | 40.43% | ||
2021 | rr_AnnualReturn2021 | 2.97% | ||
2022 | rr_AnnualReturn2022 | (33.33%) | ||
2023 | rr_AnnualReturn2023 | 9.99% | ||
2024 | rr_AnnualReturn2024 | 10.40% | ||
Highest Quarterly Return, Label | rr_HighestQuarterlyReturnLabel | Highest QuarterlyReturn | ||
Highest Quarterly Return, Date | rr_BarChartHighestQuarterlyReturnDate | Jun. 30, 2020 | ||
Highest Quarterly Return | rr_BarChartHighestQuarterlyReturn | 30.41% | ||
Lowest Quarterly Return, Label | rr_LowestQuarterlyReturnLabel | Lowest QuarterlyReturn | ||
Lowest Quarterly Return, Date | rr_BarChartLowestQuarterlyReturnDate | Mar. 31, 2020 | ||
Lowest Quarterly Return | rr_BarChartLowestQuarterlyReturn | (20.85%) | ||
1 Year | rr_AverageAnnualReturnYear01 | 10.40% | ||
5 Years | rr_AverageAnnualReturnYear05 | 3.20% | ||
10 Years | rr_AverageAnnualReturnYear10 | 4.16% | ||
William Blair Emerging Markets Growth Fund | Class I | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Maximum Sales Charge (Load) Imposed on Purchases | rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice | none | ||
Redemption Fee | rr_RedemptionFeeOverRedemption | none | ||
Management Fee | rr_ManagementFeesOverAssets | 0.94% | ||
Distribution (Rule 12b-1) Fee | rr_DistributionAndService12b1FeesOverAssets | none | ||
Other Expenses | rr_OtherExpensesOverAssets | 0.24% | ||
Total Annual Fund Operating Expenses | rr_ExpensesOverAssets | 1.18% | ||
Fee Waiver and/or Expense Reimbursement | rr_FeeWaiverOrReimbursementOverAssets | 0.19% | [1] | |
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement | rr_NetExpensesOverAssets | 0.99% | ||
1 Year | rr_ExpenseExampleYear01 | $ 101 | ||
3 Years | rr_ExpenseExampleYear03 | 356 | ||
5 Years | rr_ExpenseExampleYear05 | 631 | ||
10 Years | rr_ExpenseExampleYear10 | $ 1,415 | ||
1 Year | rr_AverageAnnualReturnYear01 | 10.62% | ||
5 Years | rr_AverageAnnualReturnYear05 | 3.44% | ||
10 Years | rr_AverageAnnualReturnYear10 | 4.42% | ||
William Blair Emerging Markets Growth Fund | Class R6 | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
Maximum Sales Charge (Load) Imposed on Purchases | rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice | none | ||
Redemption Fee | rr_RedemptionFeeOverRedemption | none | ||
Management Fee | rr_ManagementFeesOverAssets | 0.94% | ||
Distribution (Rule 12b-1) Fee | rr_DistributionAndService12b1FeesOverAssets | none | ||
Other Expenses | rr_OtherExpensesOverAssets | 0.12% | ||
Total Annual Fund Operating Expenses | rr_ExpensesOverAssets | 1.06% | ||
Fee Waiver and/or Expense Reimbursement | rr_FeeWaiverOrReimbursementOverAssets | 0.12% | [1] | |
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement | rr_NetExpensesOverAssets | 0.94% | ||
1 Year | rr_ExpenseExampleYear01 | $ 96 | ||
3 Years | rr_ExpenseExampleYear03 | 325 | ||
5 Years | rr_ExpenseExampleYear05 | 573 | ||
10 Years | rr_ExpenseExampleYear10 | $ 1,283 | ||
1 Year | rr_AverageAnnualReturnYear01 | 10.71% | ||
5 Years | rr_AverageAnnualReturnYear05 | 3.52% | ||
10 Years | rr_AverageAnnualReturnYear10 | 4.50% | ||
William Blair Emerging Markets Growth Fund | Return After Taxes on Distributions | Class N | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
1 Year | rr_AverageAnnualReturnYear01 | 10.40% | ||
5 Years | rr_AverageAnnualReturnYear05 | 2.08% | ||
10 Years | rr_AverageAnnualReturnYear10 | 3.13% | ||
William Blair Emerging Markets Growth Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class N | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
1 Year | rr_AverageAnnualReturnYear01 | 6.15% | ||
5 Years | rr_AverageAnnualReturnYear05 | 2.65% | ||
10 Years | rr_AverageAnnualReturnYear10 | 3.27% | ||
William Blair Emerging Markets Growth Fund | MSCI Emerging Markets Investable Market Index (net) (reflects no deduction for fees, expenses or taxes) | ||||
Risk/Return: | rr_RiskReturnAbstract | |||
1 Year | rr_AverageAnnualReturnYear01 | 7.09% | ||
5 Years | rr_AverageAnnualReturnYear05 | 2.51% | ||
10 Years | rr_AverageAnnualReturnYear10 | 3.90% | ||
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