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GMO Quality Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading GMO Quality Fund
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Total return.
Expense [Heading] rr_ExpenseHeading Fees and expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The table below describes the fees and expenses that you may bear for each class of shares if you buy and hold shares of the Fund.
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund operating expenses (expenses that you bear each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination Jun. 30, 2021
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may result in higher transaction costs and, for holders of Fund shares subject to U.S. taxes, higher income taxes. These transaction costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 29, 2020, the Fund’s portfolio turnover rate (excluding short-term investments) was 17% of the average value of its portfolio. That portfolio turnover rate includes investments in U.S. Treasury Fund, which the Fund uses as a short-term investment vehicle for cash management. The Fund’s portfolio turnover rate during its fiscal year ended February 29, 2020, excluding transactions in U.S. Treasury Fund and other short-term investments, was 17% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 17.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. The one year amounts shown reflect the expense reimbursement and waiver noted in the expense table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal investment strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
GMO seeks to achieve the Fund’s investment objective by investing the Fund’s assets primarily in equities of companies that GMO believes to be of high quality. GMO believes a high quality company generally to be a company that has an established business that will deliver a high level of return on past investments and that will utilize cash flows in the future by making investments with the potential for a high return on capital or by returning cash to shareholders through dividends, share buybacks, or other mechanisms.

In selecting securities for the Fund, GMO uses a combination of investment methods and typically considers both systematic factors, based on profitability, profit stability, leverage, and other publicly available financial information, and judgmental factors, based on GMO’s assessment of future profitability, capital allocation, growth opportunities, and sustainability against competitive forces. GMO also may rely on valuation methodologies, such as discounted cash flow analysis and multiples of price to earnings, revenues, book values or other fundamental metrics. In addition, GMO may consider ESG (environmental, social, and governance) criteria as well as trading patterns, such as price movement or volatility of a security or groups of securities.

The Fund is permitted to invest directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to any country in the world, including emerging countries. The term “equities” refers to direct and indirect investments in common and preferred stocks and other stock-related securities, such as convertible securities, depositary receipts, and equity real estate investment trusts (REITs) and income trusts.

At times, the Fund may have substantial exposure to a single asset class, industry, sector, country, region, currency or issuer. As of May 31, 2020, the ten largest holdings of the Fund represented approximately 43% of the Fund’s net assets. The Fund may invest in securities of companies of any market capitalization. The factors GMO considers and investment methods GMO uses can change over time. GMO does not manage the Fund to, or control the Fund’s risk relative to, any securities index or securities benchmark.

As an alternative to investing directly in equities, the Fund may invest in exchange-traded and over-the-counter (OTC) derivatives and exchange-traded funds (ETFs). The Fund also may invest in derivatives and ETFs in an attempt to obtain or adjust elements of its long or short investment exposure and as a substitute for securities lending. Derivatives used may include futures, options, forward currency contracts, and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund also may invest in U.S. Treasury Fund, in money market funds unaffiliated with GMO, and directly in the types of investments typically held by money market funds.
Risk [Heading] rr_RiskHeading Principal risks of investing in the Fund
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were a diversified investment company. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Additional Information about the Funds’ Investment Strategies, Risks, and Expenses” and “Description of Principal Risks.”

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Market Risk – Equities – The market price of an equity may decline due to factors affecting the issuer or its industry or the economy and equity markets generally. If the Fund purchases an equity for less than its fundamental fair (or intrinsic) value as assessed by GMO, the Fund runs the risk that the market price of the equity will not appreciate or will decline due to GMO’s incorrect assessment. The Fund also may purchase equities that typically trade at higher multiples of current earnings than other securities, and the market prices of these equities often are more sensitive to changes in future earnings expectations than the market prices of equities trading at lower multiples. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

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Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results. GMO uses quantitative models as part of its investment process. GMO’s models may not accurately predict future market movements or characteristics. In addition, they are based on assumptions that can limit their effectiveness, and they rely on data that is subject to limitations (e.g., inaccuracies, staleness) that could adversely affect their predictive value. The Fund also runs the risk that GMO’s assessment of an investment (including a security’s fundamental fair (or intrinsic) value) is wrong or that deficiencies in GMO’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

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Focused Investment Risk – Investments focused in asset classes, countries, regions, sectors, industries, currencies or issuers (or in sectors within a country or region) that are subject to the same or similar risk factors and investments whose prices are closely correlated are subject to greater overall risk than investments that are more diversified or whose prices are not as closely correlated. The Fund invests in the securities of a limited number of issuers, and a decline in the market price of a particular security held by the Fund may affect the Fund’s performance more than if the Fund invested in the securities of a larger number of issuers.

•

Non-U.S. Investment Risk – The market prices of many non-U.S. securities (particularly of companies tied economically to emerging countries) fluctuate more than those of U.S. securities. Many non-U.S. securities markets (particularly emerging markets) are less stable, smaller, less liquid, and less regulated than U.S. securities markets, and the cost of trading in those markets often is higher than in U.S. securities markets. In addition, issuers of non-U.S. securities (particularly those tied economically to emerging countries) often are not subject to as much regulation as U.S. issuers, and the reporting, accounting, custody, and auditing standards to which those issuers are subject often are not as rigorous as U.S. standards. Transactions in non-U.S. securities generally involve higher commission rates, transfer taxes, and custodial costs than similar transactions in U.S. securities. In addition, the Fund may be subject to non-U.S. taxes, potentially on a retroactive basis, on (i) capital gains it realizes or dividends, interest, or other amounts it realizes or accrues in respect of non-U.S. investments; (ii) transactions in those investments; and (iii) repatriation of proceeds generated from the sale or other disposition of those investments. Also, the Fund needs a license to invest directly in securities traded in many non-U.S. securities markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some non-U.S. securities markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of non-U.S. issuers, difficulties in obtaining and enforcing legal judgments) tend to be greater for investments in the securities of companies tied economically to emerging countries. The economies of emerging countries may be predominantly based on only a few industries or dependent on revenues from particular commodities, and often are more volatile than the economies of developed countries.

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Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

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Market Disruption and Geopolitical Risk – Geopolitical and other events (e.g., wars, pandemics, terrorism) may disrupt securities markets and adversely affect global economies and markets. Those events, as well as other changes in non-U.S. and U.S. economic and political conditions, could reduce the value of the Fund’s investments.

•

Counterparty Risk – The Fund runs the risk that the counterparty to a derivatives contract, a clearing member used by the Fund to hold a cleared derivatives contract, or a borrower of the Fund’s securities is unable or unwilling to make timely settlement payments, return the Fund’s margin or otherwise honor its obligations.

•

Derivatives and Short Sales Risk – The use of derivatives involves the risk that their value may not change as expected relative to changes in the value of the underlying assets, pools of assets, rates, currencies or indices. Derivatives also present other risks, including market risk, illiquidity risk, currency risk, credit risk, and counterparty risk. The market price of an option is affected by many factors, including changes in the market prices or dividend rates of underlying securities (or in the case of indices, the securities in such indices); the time remaining before expiration; changes in interest rates or exchange rates; and changes in the actual or perceived volatility of the relevant stock market and underlying securities. The Fund may create short investment exposure by taking a derivative position in which the value of the derivative moves in the opposite direction from the price of an underlying asset, pool of assets, rate, currency or index. The risks of loss associated with derivatives that provide short investment exposure and short sales of securities are theoretically unlimited.

•

Leveraging Risk – The use of derivatives and securities lending creates leverage. Leverage increases the Fund’s losses when the value of its investments (including derivatives) declines. In addition, the Fund’s portfolio will be leveraged if it exercises its right to delay payment on a redemption, and losses will result if the value of the Fund’s assets declines between the time a redemption request is deemed to be received by the Fund and the time the Fund liquidates assets to meet that request.

•

Large Shareholder Risk – To the extent that a large number of shares of the Fund is held by a single shareholder (e.g., an institutional investor or another GMO Fund) or a group of shareholders with a common investment strategy (e.g., GMO asset allocation accounts), the Fund is subject to the risk that a redemption by those shareholders of all or a large portion of their Fund shares will require the Fund to sell securities at disadvantageous prices or otherwise disrupt the Fund’s operations.

•

Smaller Company Risk – Smaller companies may have limited product lines, markets, or financial resources, lack the competitive strength of larger companies, have inexperienced managers or depend on a few key employees. The securities of companies with smaller market capitalizations often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

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Illiquidity Risk – Low trading volume, lack of a market maker, large position size, or legal restrictions may limit or prevent the Fund from selling particular securities or closing derivative positions at desirable prices.
Risk Lose Money [Text] rr_RiskLoseMoney Many factors can affect this value, and you may lose money by investing in the Fund.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were a diversified investment company.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. As of the date of this Prospectus, there are no Class R6 shares or Class I shares outstanding or such shares have not been outstanding for a full calendar year. The returns information below is for the Fund’s Class III shares. Class R6 and Class I shares would have substantially similar annual returns to Class III shares because they invest in the same portfolio of securities. Their annual returns would differ from Class III shares to the extent that they bear different expenses. While Class R6 shares are expected to bear the same expenses as Class III shares, Class I shares bear higher expenses than Class III shares and therefore would have lower returns. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-advantaged arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Updated performance information for the Fund is available at www.gmo.com. Past performance (before and after taxes) is not an indication of future performance.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.gmo.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns/​Class III Shares Years Ending December 31
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Quarter: 13.25% (1Q2019)
Lowest Quarter: -12.28% (2Q2010)
Year-to-Date (as of 3/31/20): -16.42%
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn (16.42%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 13.25%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (12.28%)
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns Periods Ending December 31, 2019
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-advantaged arrangements (such as a 401(k) plan or individual retirement account).
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.
GMO Quality Fund | Class III  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.48% [1]
Other expenses rr_OtherExpensesOverAssets 0.02%
Total annual fund operating expenses rr_ExpensesOverAssets 0.50%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.02%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.48%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 49
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 158
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 278
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 626
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 49
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 158
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 278
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 626
Annual Return 2010 rr_AnnualReturn2010 5.47%
Annual Return 2011 rr_AnnualReturn2011 11.75%
Annual Return 2012 rr_AnnualReturn2012 12.00%
Annual Return 2013 rr_AnnualReturn2013 25.36%
Annual Return 2014 rr_AnnualReturn2014 12.50%
Annual Return 2015 rr_AnnualReturn2015 1.50%
Annual Return 2016 rr_AnnualReturn2016 9.72%
Annual Return 2017 rr_AnnualReturn2017 29.06%
Annual Return 2018 rr_AnnualReturn2018 0.46%
Annual Return 2019 rr_AnnualReturn2019 31.69%
1 Year rr_AverageAnnualReturnYear01 31.69%
5 Years rr_AverageAnnualReturnYear05 13.72%
10 Years rr_AverageAnnualReturnYear10 13.48%
Since Inception rr_AverageAnnualReturnSinceInception 8.99%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 06, 2004
GMO Quality Fund | Class III | Return After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 29.17%
5 Years rr_AverageAnnualReturnYear05 10.81%
10 Years rr_AverageAnnualReturnYear10 10.88%
Since Inception rr_AverageAnnualReturnSinceInception 7.30%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 06, 2004
GMO Quality Fund | Class III | Return After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 20.30%
5 Years rr_AverageAnnualReturnYear05 10.28%
10 Years rr_AverageAnnualReturnYear10 10.47%
Since Inception rr_AverageAnnualReturnSinceInception 7.07%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 06, 2004
GMO Quality Fund | Class III | S&P 500 Index (reflects no deduction for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Since Inception rr_AverageAnnualReturnSinceInception 8.98%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 06, 2004
GMO Quality Fund | Class IV  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.435% [1]
Other expenses rr_OtherExpensesOverAssets 0.02%
Total annual fund operating expenses rr_ExpensesOverAssets 0.46%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.02%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.44%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 45
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 146
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 256
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 577
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 45
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 146
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 256
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 577
1 Year rr_AverageAnnualReturnYear01 31.79%
5 Years rr_AverageAnnualReturnYear05 13.77%
10 Years rr_AverageAnnualReturnYear10 13.53%
Since Inception rr_AverageAnnualReturnSinceInception 9.04%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 06, 2004
GMO Quality Fund | Class IV | S&P 500 Index (reflects no deduction for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Since Inception rr_AverageAnnualReturnSinceInception 8.98%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 06, 2004
GMO Quality Fund | Class V  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.415% [1]
Other expenses rr_OtherExpensesOverAssets 0.02%
Total annual fund operating expenses rr_ExpensesOverAssets 0.44%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.02%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 139
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 244
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 553
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 43
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 139
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 244
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 553
GMO Quality Fund | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.385% [1]
Other expenses rr_OtherExpensesOverAssets 0.02%
Total annual fund operating expenses rr_ExpensesOverAssets 0.41%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.02%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.39%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 40
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 130
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 228
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 516
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 40
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 130
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 228
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 516
1 Year rr_AverageAnnualReturnYear01 31.81%
5 Years rr_AverageAnnualReturnYear05 13.82%
10 Years rr_AverageAnnualReturnYear10 13.59%
Since Inception rr_AverageAnnualReturnSinceInception 10.05%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 08, 2006
GMO Quality Fund | Class VI | S&P 500 Index (reflects no deduction for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Since Inception rr_AverageAnnualReturnSinceInception 8.83%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 08, 2006
GMO Quality Fund | Class R6  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.48% [1]
Other expenses rr_OtherExpensesOverAssets 0.02%
Total annual fund operating expenses rr_ExpensesOverAssets 0.50%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.02%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.48%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 49
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 158
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 278
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 626
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 49
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 158
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 278
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 626
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess As of the date of this Prospectus, there are no Class R6 shares or Class I shares outstanding or such shares have not been outstanding for a full calendar year.
GMO Quality Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.48% [1]
Other expenses rr_OtherExpensesOverAssets 0.12% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.60%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.02%) [1],[2]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.58%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 59
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 190
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 333
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 748
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 59
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 190
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 333
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 748
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess As of the date of this Prospectus, there are no Class R6 shares or Class I shares outstanding or such shares have not been outstanding for a full calendar year.
[1] Includes both management fee of 0.33% and class-specific shareholder service fee, if any, for each class of shares. For additional information about the shareholder service fee applicable to each class of shares of the Fund, please see the table included in the section of the Prospectus entitled "Multiple Classes and Eligibility." Grantham, Mayo, Van Otterloo & Co. LLC ("GMO") has contractually agreed to reimburse the Fund for the following expenses: audit expenses, fund accounting expenses, pricing service expenses, expenses of non-investment related tax services, transfer agency expenses (excluding, in the case of Class I shares, any amounts paid for sub-transfer agency, recordkeeping and other administrative services provided by financial intermediaries with respect to Class I shareholders), expenses of non-investment related legal services provided to the Fund by or at the direction of GMO, federal securities law filing expenses, printing expenses, state and federal registration fees and custody expenses. GMO also has contractually agreed to waive or reduce the Fund's management fees and shareholder service fees to the extent necessary to offset the management fees and shareholder service fees paid to GMO that are directly or indirectly borne by the Fund or a class of shares of the Fund as a result of the Fund's direct or indirect investments in other series of GMO Trust ("GMO Funds"). Management fees and shareholder service fees will not be waived below zero. These reimbursements and waivers will continue through at least June 30, 2021 and may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.
[2] Includes estimate of payments for sub-transfer agency, recordkeeping and other administrative services for Class I's initial fiscal year. GMO has contractually agreed to waive its fees with respect to and/or reimburse Class I shares to the extent that amounts paid by the Fund out of the net assets attributable to Class I shares for sub-transfer agency, recordkeeping and other administrative services provided by financial intermediaries with respect to Class I shareholders exceed 0.10% of the average daily net assets attributable to Class I shares. This reimbursement will continue through at least June 30, 2021 and may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.