Shareholder Fees - William Blair Global Leaders Fund	Dec. 31, 2025
Class N
Prospectus [Line Items]
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	0.00%
Redemption Fee (as a percentage of Amount Redeemed)	0.00%
Class I
Prospectus [Line Items]
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	0.00%
Redemption Fee (as a percentage of Amount Redeemed)	0.00%
Class R6
Prospectus [Line Items]
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	0.00%
Redemption Fee (as a percentage of Amount Redeemed)	0.00%