S000066499 [Member] Expense Example - William Blair Small-Mid Cap Core Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 97 |
| Expense Example, with Redemption, 3 Years | 354 |
| Expense Example, with Redemption, 5 Years | 631 |
| Expense Example, with Redemption, 10 Years | 1,422 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 92 |
| Expense Example, with Redemption, 3 Years | 317 |
| Expense Example, with Redemption, 5 Years | 560 |
| Expense Example, with Redemption, 10 Years | $ 1,258 |