Prospectus:
Risk/Return:
Legal Entity Identifier
Entity Inv Company Type
Document Type
Document Period End Date
Registrant Name
Entity Central Index Key
Amendment Flag
Amendment Description
Trading Symbol
Document Creation Date
Document Effective Date
Prospectus Date
Performance Measure [Axis]
Share Class [Axis]
Document [Axis]
Prospectus
Coregistrant [Axis]
Coregistrant [Domain]
Series [Axis]
Series
S000008594 [Member]
William Blair Growth Fund
William Blair Growth Fund Member
Return After Taxes on Distributions
After Taxes on Distributions
Return After Taxes on Distributions and Sale of Fund Shares
After Taxes on Distributions and Sales
Before Taxes
Russell Three Thousand
Russell Three Thousand [Member]
Russell 3000® Growth Index (reflects no deduction for fees, expenses or taxes)
S And P Five Hundred
S And P Five Hundred [Member]
S&P 500® Index (reflects no deduction for fees, expenses or taxes)
Share Classes
C000023523 [Member]
Class N
Class N
C000023524 [Member]
Class I
Class I
C000211716 [Member]
Class R6
Class R6
Maximum Sales Charge (Load) Imposed on Purchases
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)
Redemption Fee
Redemption Fee (as a percentage of Amount Redeemed)
Management Fee
Management Fees (as a percentage of Assets)
Distribution (Rule 12b-1) Fee
Distribution and Service (12b-1) Fees
Other Expenses
Other Expenses (as a percentage of Assets):
Total Annual Fund Operating Expenses
Expenses (as a percentage of Assets)
Fee Waiver and/or Expense Reimbursement
Fee Waiver or Reimbursement
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement
Net Expenses (as a percentage of Assets)
1 Year
Expense Example, with Redemption, 1 Year
3 Years
Expense Example, with Redemption, 3 Years
5 Years
Expense Example, with Redemption, 5 Years
10 Years
Expense Example, with Redemption, 10 Years
2013
Annual Return 2013
2014
Annual Return 2014
2015
Annual Return 2015
2016
Annual Return 2016
2017
Annual Return 2017
2018
Annual Return 2018
2019
Annual Return 2019
2020
Annual Return 2020
2021
Annual Return 2021
2022
Annual Return 2022
1 Year
1 Year
5 Years
5 Years
10 Years
10 Years
Since Share Class Inception
Since Inception
Since Fund Inception
Inception Date
Inception Date
Risk/Return [Heading]
Objective [Heading]
Objective, Primary [Text Block]
Objective, Secondary [Text Block]
Expense [Heading]
Expense Narrative [Text Block]
Shareholder Fees Caption [Text]
Shareholder Fees Column [Text]
Maximum Cumulative Sales Charge (as a percentage of Offering Price)
Maximum Cumulative Sales Charge (as a percentage)
Maximum Deferred Sales Charge (as a percentage of Offering Price)
Maximum Deferred Sales Charge (as a percentage)
Maximum Sales Charge on Reinvested Dividends and Distributions (as a percentage)
Redemption Fee
Redemption Fee
Exchange Fee (as a percentage of Amount Redeemed)
Exchange Fee
Maximum Account Fee (as a percentage of Assets)
Maximum Account Fee
Shareholder Fee, Other
Operating Expenses Caption [Text]
Operating Expenses Column [Text]
Distribution or Similar (Non 12b-1) Fees
Component1 Other Expenses
Component2 Other Expenses
Component3 Other Expenses
Acquired Fund Fees and Expenses
Fee Waiver or Reimbursement over Assets, Date of Termination
Portfolio Turnover [Heading]
Portfolio Turnover [Text Block]
Portfolio Turnover, Rate
Expenses Deferred Charges [Text Block]
Expenses Range of Exchange Fees [Text Block]
Expense Breakpoint Discounts [Text]
Expense Breakpoint, Minimum Investment Required [Amount]
Expenses Represent Both Master and Feeder [Text]
Expenses Explanation of Nonrecurring Account Fee [Text]
Other Expenses, New Fund, Based on Estimates [Text]
Acquired Fund Fees and Expenses, Based on Estimates [Text]
Expenses Restated to Reflect Current [Text]
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]
Expense Example [Heading]
Expense Example by Year [Heading]
Expense Example Narrative [Text Block]
Expense Example by, Year, Caption [Text]
Expense Example, No Redemption Narrative [Text Block]
Expense Example, No Redemption, By Year, Caption [Text]
1 Year
Expense Example, No Redemption, 1 Year
3 Years
Expense Example, No Redemption, 3 Years
5 Years
Expense Example, No Redemption, 5 Years
10 Years
Expense Example, No Redemption, 10 Years
Expense Example Closing [Text Block]
Strategy [Heading]
Strategy Narrative [Text Block]
Strategy Portfolio Concentration [Text]
Risk [Heading]
Risk Narrative [Text Block]
Risk Closing [Text Block]
Risk Lose Money [Text]
Risk Money Market Fund Price Fluctuates [Text]
Risk Money Market Fund May Not Preserve Dollar [Text]
Risk Money Market Fund May Impose Fees or Suspend Sales [Text]
Risk Not Insured Depository Institution [Text]
RIsk Not Insured [Text]
Risk Nondiversified Status [Text]
Risk Caption
Risk Column [Text]
Risk [Text]
Bar Chart and Performance Table [Heading]
Performance Narrative [Text Block]
Performance Information Illustrates Variability of Returns [Text]
Performance One Year or Less [Text]
Performance Additional Market Index [Text]
Performance Availability Phone [Text]
Performance Availability Website Address [Text]
Performance Past Does Not Indicate Future [Text]
Bar Chart [Heading]
Bar Chart Narrative [Text Block]
Bar Chart Does Not Reflect Sales Loads [Text]
Annual Return Caption [Text]
Caption
Annual Return, Column [Text]
Column
Annual Return, Inception Date
Inception Date
Annual Return 1990
Annual Return 1991
Annual Return 1992
Annual Return 1993
Annual Return 1994
Annual Return 1995
Annual Return 1996
Annual Return 1997
Annual Return 1998
Annual Return 1999
Annual Return 2000
Annual Return 2001
Annual Return 2002
Annual Return 2003
Annual Return 2004
Annual Return 2005
Annual Return 2006
Annual Return 2007
Annual Return 2008
Annual Return 2009
Annual Return 2010
Annual Return 2011
Annual Return 2012
Annual Return 2023
Annual Return 2024
Annual Return 2025
Bar Chart Closing [Text Block]
Bar Chart, Reason Selected Class Different from Immediately Preceding Period [Text]
Bar Chart, Returns for Class Not Offered in Prospectus [Text]
Year to Date Return, Label
Bar Chart, Year to Date Return, Date
Bar Chart, Year to Date Return
Highest Quarterly Return, Label
Label
Highest Quarterly Return, Date
Highest Quarterly Return
Label
Lowest Quarterly Return, Label
Lowest Quarterly Return, Date
Lowest Quarterly Return
Performance Table Heading
Performance Table Does Reflect Sales Loads
Performance Table Market Index Changed
Index No Deduction for Fees, Expenses, Taxes [Text]
Performance Table Uses Highest Federal Rate
Performance Table Not Relevant to Tax Deferred
Performance Table One Class of after Tax Shown [Text]
Performance Table Explanation after Tax Higher
Performance Table Narrative
Performance Table Closing [Text Block]
Average Annual Return, Caption
Average Annual Return, Column Name
Label
Money Market Seven Day Yield, Caption [Text]
Money Market Seven Day Yield Column [Text]
Money Market Seven Day Yield Phone
Money Market Seven Day Yield
Money Market Seven Day Tax Equivalent Yield
Thirty Day Yield Caption
Thirty Day Yield Column [Text]
Thirty Day Yield Phone
Thirty Day Yield
Thirty Day Tax Equivalent Yield
Supplement to Prospectus [Text Block]
S000008601 [Member]
William Blair Large Cap Growth Fund
William Blair Large Cap Growth Fund Member
Russell Thousand Growth
Russell Thousand Growth [Member]
Russell 1000® Growth Index (reflects no deduction for fees, expenses or taxes)
C000023538 [Member]
Class N
Class N
C000023539 [Member]
Class I
Class I
C000211719 [Member]
Class R6
Class R6
S000010050 [Member]
William Blair Mid Cap Growth Fund
William Blair Mid Cap Growth Fund Member
Russell Midcap One
Russell Midcap One [Member]
Russell Midcap® Growth Index (reflects no deduction for fees, expenses or taxes)
C000027836 [Member]
Class N
Class N
C000027837 [Member]
Class I
Class I
C000211724 [Member]
Class R6
Class R6
S000075391 [Member]
William Blair Mid Cap Value Fund
William Blair Mid Cap Value Fund Member
C000234386 [Member]
Class I
Class I
C000234387 [Member]
Class R6
Class R6
S000066499 [Member]
William Blair Small-Mid Cap Core Fund
William Blair Small-Mid Cap Core Fund Member
Russell Twothousand Five Hundred Tm
Russell Twothousand Five Hundred Tm [Member]
Russell 2500™ Index (reflects no deduction for fees, expenses or taxes)
C000214491 [Member]
Class I
Class I
C000214492 [Member]
Class R6
Class R6
S000008603 [Member]
William Blair Small-Mid Cap Growth Fund
William Blair Small-Mid Cap Growth Fund Member
Russell 2500TM Growth Index
Russell 2500TM Growth Index [Member]
Russell 2500™ Growth Index (reflects no deduction for fees, expenses or taxes)
Russell One
Russell One [Member]
Russell 2500 ™ Growth Index (reflects no deduction for fees, expenses or taxes)
C000023542 [Member]
Class N
Class N
C000023543 [Member]
Class I
Class I
C000211721 [Member]
Class R6
Class R6
S000008602 [Member]
William Blair Small Cap Growth Fund
William Blair Small Cap Growth Fund Member
Russell Two Thousand Growth One
Russell Two Thousand Growth One [Member]
Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)
C000023540 [Member]
Class N
Class N
C000023541 [Member]
Class I
Class I
C000211720 [Member]
Class R6
Class R6
S000008597 [Member]
William Blair Small Cap Value Fund
William Blair Small Cap Value Fund Member
Russell Two Thousand Value One
Russell Two Thousand Value One [Member]
Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)
C000023531 [Member]
Class N
Class N
C000023532 [Member]
Class I
Class I
C000211717 [Member]
Class R6
Class R6
S000019315 [Member]
William Blair Global Leaders Fund
William Blair Global Leaders Fund Member
Msci All One
Msci All One [Member]
MSCI All Country World IMI (net) (reflects no deduction for fees, expenses or taxes)
C000053607 [Member]
Class N
Class N
C000053608 [Member]
Class I
Class I
C000053609 [Member]
Class R6
Class R6
S000037763 [Member]
William Blair International Leaders Fund
William Blair International Leaders Fund Member
Msci All Country World Ex Us Imi
Msci All Country World Ex Us Imi [Member]
MSCI All Country World Ex-US IMI (net) (reflects no deduction for fees, expenses or taxes)
C000116468 [Member]
Class N
Class N
C000116469 [Member]
Class I
Class I
C000116470 [Member]
Class R6
Class R6
S000008604 [Member]
William Blair International Growth Fund
William Blair International Growth Fund Member
Msci All Country World Ex Us Imi One
Msci All Country World Ex Us Imi One [Member]
MSCI All Country World Ex-U.S. IMI (net) (reflects no deduction for fees, expenses or taxes)
C000023544 [Member]
Class N
Class N
C000023545 [Member]
Class I
Class I
C000211722 [Member]
Class R6
Class R6
S000008605 [Member]
William Blair Institutional International Growth Fund
William Blair Institutional International Growth Fund Member
C000023546 [Member]
Institutional Class
Institutional Class
S000008595 [Member]
William Blair International Small Cap Growth Fund
William Blair International Small Cap Growth Fund Member
Msci All Country World Ex Us Small Cap Index
Msci All Country World Ex Us Small Cap Index [Member]
MSCI All Country World Ex-U.S. Small Cap Index (net) (reflects no deduction for fees, expenses or taxes)
C000023525 [Member]
Class N
Class N
C000023526 [Member]
Class I
Class I
C000023527 [Member]
Class R6
Class R6
S000021052 [Member]
William Blair Emerging Markets Leaders Fund
William Blair Emerging Markets Leaders Fund Member
Msci Emerging Markets Index
Msci Emerging Markets Index [Member]
MSCI Emerging Markets Index (net) (reflects no deduction for fees, expenses or taxes)
C000088850 [Member]
Class N
Class N
C000059867 [Member]
Class I
Class I
C000059868 [Member]
Class R6
Class R6
S000008596 [Member]
William Blair Emerging Markets Growth Fund
William Blair Emerging Markets Growth Fund Member
Msci Emerging Markets Imi
Msci Emerging Markets Imi [Member]
MSCI Emerging Markets IMI (net) (reflects no deduction for fees, expenses or taxes)
C000023528 [Member]
Class N
Class N
C000023529 [Member]
Class I
Class I
C000023530 [Member]
Class R6
Class R6
S000075390 [Member]
William Blair Emerging Markets ex China Growth Fund
William Blair Emerging Markets ex China Growth Fund Member
C000234384 [Member]
Class I
Class I
C000234385 [Member]
Class R6
Class R6
S000034349 [Member]
William Blair Emerging Markets Small Cap Growth Fund
William Blair Emerging Markets Small Cap Growth Fund Member
Msci Emerging Markets Small Cap Index
Msci Emerging Markets Small Cap Index [Member]
MSCI Emerging Markets Small Cap Index (net) (reflects no deduction for fees, expenses or taxes)
C000105754 [Member]
Class N
Class N
C000105753 [Member]
Class I
Class I
C000105755 [Member]
Class R6
Class R6
S000072753 [Member]
William Blair China Growth Fund
William Blair China Growth Fund Member
Msci China One
Msci China One [Member]
MSCI China All Shares Index (reflects no deduction for fees, expenses or taxes)
C000229252 [Member]
Class I
Class I
C000229253 [Member]
Class R6
Class R6
S000069167 [Member]
William Blair Emerging Markets Debt Fund
William Blair Emerging Markets Debt Fund Member
Jpmorgan Emerging Markets Bond Index Global Diversified
Jpmorgan Emerging Markets Bond Index Global Diversified [Member]
JPMorgan Emerging Markets Bond Index (EMBI) Global Diversified (reflects no deduction for fees, expenses or taxes)
C000221009 [Member]
Class I
Class I
C000221008 [Member]
Class R6
Class R6
S000028811 [Member]
William Blair Mid Cap Value Fund
William Blair Mid Cap Value Fund Member
C000088322 [Member]
Class I
Class I
C000088323 [Member]
Class N
Class N