v3.26.1
S000008595 [Member] Annual Fund Operating Expenses - William Blair International Small Cap Growth Fund
Dec. 31, 2025
Prospectus [Line Items]  
Fee Waiver or Reimbursement over Assets, Date of Termination April 30, 2027
Class N  
Prospectus [Line Items]  
Management Fees (as a percentage of Assets) 1.00%
Distribution and Service (12b-1) Fees 0.25%
Other Expenses (as a percentage of Assets): 0.36%
Expenses (as a percentage of Assets) 1.61%
Fee Waiver or Reimbursement 0.26% [1]
Net Expenses (as a percentage of Assets) 1.35% [2]
Class I  
Prospectus [Line Items]  
Management Fees (as a percentage of Assets) 1.00%
Distribution and Service (12b-1) Fees 0.00%
Other Expenses (as a percentage of Assets): 0.34%
Expenses (as a percentage of Assets) 1.34%
Fee Waiver or Reimbursement 0.24% [1]
Net Expenses (as a percentage of Assets) 1.10% [2]
Class R6  
Prospectus [Line Items]  
Management Fees (as a percentage of Assets) 1.00%
Distribution and Service (12b-1) Fees 0.00%
Other Expenses (as a percentage of Assets): 0.23%
Expenses (as a percentage of Assets) 1.23%
Fee Waiver or Reimbursement 0.18% [1]
Net Expenses (as a percentage of Assets) 1.05% [2]
[1]
William Blair Investment Management, LLC (the “Adviser”) has entered into a contractual agreement with the Fund to waive fees and/or reimburse expenses in order to limit the Fund’s operating expenses (excluding interest expenses, taxes, brokerage commissions, acquired fund fees and expenses, dividend and interest expenses on short sales, other investment-related costs and extraordinary expenses, such as litigation and other expenses not incurred in the ordinary course of the Fund’s business) to 1.35%, 1.10% and 1.05% of average daily net assets for Class N, Class I and Class R6 shares, respectively, until April 30, 2027. The Adviser may not terminate this arrangement prior to April 30, 2027 without the approval of the Fund’s Board of Trustees.
[2]
The Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement does not equal the net expense ratio to average daily net assets in the Financial Highlights section of this Prospectus as a result of a change in the contractual expense limits.