S000075391 [Member] Expense Example - William Blair Mid Cap Value Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 77 |
| Expense Example, with Redemption, 3 Years | 1,924 |
| Expense Example, with Redemption, 5 Years | 3,618 |
| Expense Example, with Redemption, 10 Years | 7,261 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 72 |
| Expense Example, with Redemption, 3 Years | 1,914 |
| Expense Example, with Redemption, 5 Years | 3,605 |
| Expense Example, with Redemption, 10 Years | $ 7,246 |