v3.26.1
GMO Benchmark-Free Allocation Fund Average Annual Total Returns
 12 Months Ended 56 Months Ended 60 Months Ended 65 Months Ended 120 Months Ended 145 Months Ended 257 Months Ended
Feb. 28, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Bloomberg U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   1.25%   (0.33%)   1.35%    
MSCI World Index (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]   18.67%   11.16%   9.95%    
Class III                
Prospectus [Line Items]                
Average Annual Return, Percent [2]   4.27%   3.02%   3.21%   6.79%
Performance Inception Date Jul. 23, 2003              
Class III | After Taxes on Distributions                
Prospectus [Line Items]                
Average Annual Return, Percent [2]   2.95%   1.92%   2.24%   5.27%
Class III | After Taxes on Distributions and Sales                
Prospectus [Line Items]                
Average Annual Return, Percent [2]   3.29%   2.12%   2.26%   5.13%
Class III | Consumer Price Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   2.86%   4.21%   3.01%   2.59%
Class III | Bloomberg U.S. Treasury Inflation Notes: 1-10 Year Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   3.09%   2.69%   2.53%   3.39%
Class III | Bloomberg U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   1.25%   (0.33%)   1.35%   3.10%
Class III | MSCI World Index (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]   18.67%   11.16%   9.95%   8.94%
Class IV                
Prospectus [Line Items]                
Average Annual Return, Percent   4.36%   3.09%   3.27% 3.77%  
Performance Inception Date Dec. 11, 2012              
Class IV | Consumer Price Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   2.86%   4.21%   3.01% 2.68%  
Class IV | Bloomberg U.S. Treasury Inflation Notes: 1-10 Year Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   3.09%   2.69%   2.53% 1.64%  
Class IV | Bloomberg U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent             1.42%  
Class IV | MSCI World Index (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]             10.84%  
Class R6                
Prospectus [Line Items]                
Average Annual Return, Percent   4.29% 5.96%      
Performance Inception Date May 01, 2020              
Class R6 | Consumer Price Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   2.86% 4.74%          
Class R6 | Bloomberg U.S. Treasury Inflation Notes: 1-10 Year Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   3.09% 2.43%          
Class R6 | Bloomberg U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent     (1.36%)          
Class R6 | MSCI World Index (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]     15.82%          
Class I                
Prospectus [Line Items]                
Average Annual Return, Percent   4.16%   2.92% 3.89%    
Performance Inception Date Aug. 08, 2019              
Class I | Consumer Price Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   2.86%   4.21% 4.06%      
Class I | Bloomberg U.S. Treasury Inflation Notes: 1-10 Year Index (returns reflect no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent   3.09%   2.69% 2.59%      
Class I | Bloomberg U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes)[Member]                
Prospectus [Line Items]                
Average Annual Return, Percent         (0.15%)      
Class I | MSCI World Index (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]         12.38%      
[1] 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.
[2] The returns shown for periods prior to January 1, 2012 are for Class III shares of the Fund under the Fund’s prior fee arrangement. Under the Fund’s current fee arrangement, the returns for periods prior to January 1, 2012 would have been lower.