S000080810 [Member] Expense Example - William Blair Small-Mid Cap Value Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 87 |
| Expense Example, with Redemption, 3 Years | 1,136 |
| Expense Example, with Redemption, 5 Years | 2,185 |
| Expense Example, with Redemption, 10 Years | 4,803 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 82 |
| Expense Example, with Redemption, 3 Years | 1,122 |
| Expense Example, with Redemption, 5 Years | 2,162 |
| Expense Example, with Redemption, 10 Years | $ 4,763 |