S000008597 [Member] Expense Example - William Blair Small Cap Value Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class N | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | $ 117 |
| Expense Example, with Redemption, 3 Years | 367 |
| Expense Example, with Redemption, 5 Years | 637 |
| Expense Example, with Redemption, 10 Years | 1,408 |
| Class I | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 91 |
| Expense Example, with Redemption, 3 Years | 292 |
| Expense Example, with Redemption, 5 Years | 511 |
| Expense Example, with Redemption, 10 Years | 1,139 |
| Class R6 | |
| Prospectus [Line Items] | |
| Expense Example, with Redemption, 1 Year | 82 |
| Expense Example, with Redemption, 3 Years | 255 |
| Expense Example, with Redemption, 5 Years | 444 |
| Expense Example, with Redemption, 10 Years | $ 990 |