RULE 497 DOCUMENT
On behalf of William Blair Emerging Leaders Growth Fund and William Blair Global Growth Fund, each a series of William Blair Funds (the “Funds”), and pursuant to Rule 497(e) under the Securities Act of 1933, as amended (the “Securities Act”), the purpose of this filing is to submit an interactive data file in the manner provided by Rule 405 of Regulation S-T and General Instruction C.3(g) of Form N-1A. The interactive data file included as an exhibit to this filing relates to the supplement filed with the Securities and Exchange Commission on behalf of the Funds pursuant to Rule 497(e) under the Securities Act on December 10, 2012; such supplement (accession number 0001193125-12-497008) is incorporated by reference into this Rule 497 Document.
WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary – Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary – Fund Performance History – Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary—Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary—Fund Performance History—Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary – Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary – Fund Performance History – Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. |
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| Registrant Name | dei_EntityRegistrantName | WILLIAM BLAIR FUNDS | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Prospectus Date | rr_ProspectusDate | May 01, 2012 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Supplement [Text Block] | wbf2_SupplementTextBlock | WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary – Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary – Fund Performance History – Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary—Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary—Fund Performance History—Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary – Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary – Fund Performance History – Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. |
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Class N | William Blair Emerging Leaders Growth Fund
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| Risk/Return: | rr_RiskReturnAbstract | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Supplement [Text Block] | wbf2_SupplementTextBlock | WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary – Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary – Fund Performance History – Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. |
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Class I | William Blair Emerging Leaders Growth Fund
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| Risk/Return: | rr_RiskReturnAbstract | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Supplement [Text Block] | wbf2_SupplementTextBlock | WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary—Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary—Fund Performance History—Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. |
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Institutional Class | William Blair Emerging Leaders Growth Fund
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| Supplement [Text Block] | wbf2_SupplementTextBlock | WILLIAM BLAIR EMERGING LEADERS GROWTH FUND Effective December 31, 2012, the name of the William Blair Emerging Leaders Growth Fund will change to the William Blair Emerging Markets Leaders Fund. On that date, all references to the William Blair Emerging Leaders Growth Fund in the prospectus will refer to the William Blair Emerging Markets Leaders Fund. The paragraph below replaces the disclosure for the Fund in the Prospectus under "Summary – Fund Performance History." FUND PERFORMANCE HISTORY: The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund’s performance and by showing how the Fund’s average annual returns for the years indicated compare with that of a broad measure of market performance. Effective December 31, 2012, the Fund will compare its performance to the MSCI Emerging Markets Index as the Advisor believes that the MSCI Emerging Markets Index represents a broader universe of the kinds of companies in which the Fund may invest. 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.williamblair.com or call 1-800-635-2886. The table below replaces the Average Annual Total Returns table for the Fund in the Prospectus under "Summary – Fund Performance History – Average Annual Total Returns (For the periods ended December 31, 2011)."
The paragraph below replaces the first paragraph of the disclosure in the Prospectus under "Summary – Principal Investment Strategies." 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 Advisor believes have above-average growth, profitability and quality characteristics. Under normal market conditions, the Fund typically holds a limited number of securities (i.e., 50-80 securities). The Advisor seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development, although the Fund’s assets primarily will be invested in securities of companies that have a float adjusted market capitalization greater than $3 billion. Securities of companies whose float adjusted market capitalization falls below $3 billion after purchase may continue to be held in the Fund. 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. The Fund may invest in equity securities through initial public offerings (IPOs) and private placements. |
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Document and Entity Information
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12 Months Ended |
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May 01, 2012
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| Risk/Return: | |
| Document Type | Other |
| Document Period End Date | Dec. 31, 2011 |
| Registrant Name | WILLIAM BLAIR FUNDS |
| Central Index Key | 0000822632 |
| Amendment Flag | false |
| Document Creation Date | Dec. 10, 2012 |
| Document Effective Date | Dec. 10, 2012 |
| Prospectus Date | May 01, 2012 |
| Label | Element | Value |
|---|---|---|
| Risk/Return: | rr_RiskReturnAbstract | |
| Registrant Name | dei_EntityRegistrantName | WILLIAM BLAIR FUNDS |
| Prospectus Date | rr_ProspectusDate | May 01, 2012 |
| Document Creation Date | dei_DocumentCreationDate | Dec. 10, 2012 |