S000008605 [Member] Investment Objectives and Goals - William Blair Institutional International Growth Fund |
Dec. 31, 2025 |
|---|---|
| Prospectus [Line Items] | |
| Risk/Return [Heading] | WILLIAM BLAIR INSTITUTIONAL INTERNATIONAL GROWTH FUND SUMMARY |
| Objective [Heading] | INVESTMENT OBJECTIVE: |
| Objective, Primary [Text Block] | The William Blair Institutional International Growth Fund seeks long-term capital appreciation. |