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GMO International Equity Allocation Fund Average Annual Total Returns
 12 Months Ended 60 Months Ended 76 Months Ended 120 Months Ended 351 Months Ended
Feb. 28, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Class III            
Prospectus [Line Items]            
Average Annual Return, Percent [1]   40.90% 9.96%   9.07% 7.39%
Performance Inception Date Oct. 11, 1996          
Class III | After Taxes on Distributions            
Prospectus [Line Items]            
Average Annual Return, Percent [1]   38.28% 8.22%   7.82% 5.89%
Class III | After Taxes on Distributions and Sales            
Prospectus [Line Items]            
Average Annual Return, Percent [1]   25.03% 7.35%   7.07% 5.78%
Class III | MSCI ACWI ex USA (Fund benchmark) (returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent [1],[2]   32.39% 7.91%   8.41% 5.92%
Class R6            
Prospectus [Line Items]            
Average Annual Return, Percent [1]   40.88% 9.96% 11.54%  
Performance Inception Date Aug. 30, 2019          
Class R6 | MSCI ACWI ex USA (Fund benchmark) (returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent [1],[2]   32.39% 7.91% 9.80%    
[1] Returns include a substantial, one-time litigation settlement recovery received on December 16, 2024. This event contributed 2.51% to 2024 annual performance.
[2] MSCI data may not be reproduced or used for any other purpose. MSCI provides no warranties, has not prepared or approved this report, and has no liability hereunder.