S000008604 [Member] Expense Example - William Blair International Growth Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class N | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 117 |
| Expense Example, with Redemption, 3 Years | 399 |
| Expense Example, with Redemption, 5 Years | 703 |
| Expense Example, with Redemption, 10 Years | 1,565 |
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 92 |
| Expense Example, with Redemption, 3 Years | 315 |
| Expense Example, with Redemption, 5 Years | 556 |
| Expense Example, with Redemption, 10 Years | 1,248 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 87 |
| Expense Example, with Redemption, 3 Years | 286 |
| Expense Example, with Redemption, 5 Years | 502 |
| Expense Example, with Redemption, 10 Years | $ 1,125 |