STOCK-BASED COMPENSATION - 2024 employee stock purchase plan (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] | |||
| Balance as of December 31, 2024 | 479,339 | ||
| Balance as of December 31, 2025 | 513,386 | 479,339 | |
| Issuance of common stock under ESPP | $ 4,525 | $ 0 | $ 0 |
| The GRAIL, Inc. 2024 Employee Stock Purchase Plan | |||
| Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] | |||
| Balance as of December 31, 2024 | 414,021 | ||
| Annual increase | 338,934 | ||
| Issued | (136,551) | ||
| Balance as of December 31, 2025 | 616,404 | 414,021 | |
| Issuance of common stock under ESPP | $ 4,500 | ||