| Document and Entity Information | Jun. 03, 2024 |
| Cover [Abstract] | |
| Amendment Flag | true |
| Entity Central Index Key | 0001699031 |
| Document Type | 8-K/A |
| Document Period End Date | Jun. 03, 2024 |
| Entity Registrant Name | GRAIL, LLC |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-42045 |
| Entity Tax Identification Number | 86-3673636 |
| Entity Address, Address Line One | 1525 O’Brien Drive |
| Entity Address, City or Town | Menlo Park |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94025 |
| City Area Code | (833) |
| Local Phone Number | 694-2553 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common stock, par value $0.001 per share |
| Trading Symbol | GRAL |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Amendment Description | On June 3, 2024, GRAIL, LLC (the “Company” or “GRAIL”) filed a Current Report on Form 8-K (the “Original 8-K”) to announce that a registration statement on Form 10, initially filed on May 6, 2024, relating to the separation (the “Spin-Off”) of the Company from Illumina, Inc. (“Illumina”), to be effected by Illumina’s distribution of at least 85.5% of the shares of common stock of the Company, par value $0.001 per share, to holders of common stock of Illumina as a pro rata dividend in the Spin-Off (the “Distribution”), was declared effective by the U.S. Securities and Exchange Commission. The Original 8-K also included information regarding anticipated dates affecting the trading of GRAIL’s common stock in connection with the Distribution. This Form 8-K/A is being filed to further clarify those dates. |
