v3.25.4
STOCK-BASED COMPENSATION - Restricted stock units (Details)
shares in Thousands, $ in Millions
12 Months Ended
Dec. 31, 2025
USD ($)
award
shares
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
2024 Transition Incentive Award Plan      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share Based Payment Arrangement By Share Based Payment Award, Number Of Performance Plans | award 2    
Performance Shares      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Aggregate potential fair value $ 1.6    
Performance Shares | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award One      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, options, nonvested, number of shares | shares 26,000    
Performance Shares | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award Two      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, options, nonvested, number of shares | shares 5,000    
Performance Shares | Tranche One | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award One      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage 33.33%    
Performance Shares | Tranche One | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award Two      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage 60.00%    
Performance Shares | Tranche Two | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award One      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage 33.33%    
Performance Shares | Tranche Two | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award Two      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage 40.00%    
Performance Shares | Tranche Three | The GRAIL, Inc. 2024 Incentive Award Plan, PSU Award One      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage 33.33%    
Restricted Stock Units (RSUs)      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Fair value of replacement awards $ 416.2 $ 98.6  
Fair value of restricted stock vested $ 93.8 $ 45.5 $ 0.5