S000008594 [Member] Expense Example - William Blair Growth Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class N | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 122 |
| Expense Example, with Redemption, 3 Years | 392 |
| Expense Example, with Redemption, 5 Years | 682 |
| Expense Example, with Redemption, 10 Years | 1,507 |
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 93 |
| Expense Example, with Redemption, 3 Years | 290 |
| Expense Example, with Redemption, 5 Years | 504 |
| Expense Example, with Redemption, 10 Years | 1,120 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 89 |
| Expense Example, with Redemption, 3 Years | 278 |
| Expense Example, with Redemption, 5 Years | 482 |
| Expense Example, with Redemption, 10 Years | $ 1,073 |