S000008595 [Member] Expense Example - William Blair International Small Cap Growth Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class N | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 137 |
| Expense Example, with Redemption, 3 Years | 483 |
| Expense Example, with Redemption, 5 Years | 852 |
| Expense Example, with Redemption, 10 Years | 1,889 |
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 112 |
| Expense Example, with Redemption, 3 Years | 401 |
| Expense Example, with Redemption, 5 Years | 711 |
| Expense Example, with Redemption, 10 Years | 1,592 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 107 |
| Expense Example, with Redemption, 3 Years | 373 |
| Expense Example, with Redemption, 5 Years | 658 |
| Expense Example, with Redemption, 10 Years | $ 1,473 |