S000021052 [Member] Expense Example - William Blair Emerging Markets Leaders Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 101 |
| Expense Example, with Redemption, 3 Years | 375 |
| Expense Example, with Redemption, 5 Years | 670 |
| Expense Example, with Redemption, 10 Years | 1,509 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 96 |
| Expense Example, with Redemption, 3 Years | 351 |
| Expense Example, with Redemption, 5 Years | 626 |
| Expense Example, with Redemption, 10 Years | 1,410 |
| Class N | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 126 |
| Expense Example, with Redemption, 3 Years | 457 |
| Expense Example, with Redemption, 5 Years | 811 |
| Expense Example, with Redemption, 10 Years | $ 1,809 |