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GMO High Yield Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading GMO High Yield Fund
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Total return in excess of that of its benchmark, the Markit iBoxx USD Liquid High Yield Index.
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 214% 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 105% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 105.00%
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
The Fund’s investment objective is total return (which is net of fees) in excess of the Markit iBoxx USD Liquid High Yield Index. GMO seeks to achieve the Fund’s investment objective by applying a systematic, factor-based approach to portfolio construction. Through its research, GMO has identified factors that it believes affect returns across the high yield asset class. GMO uses quantitative models, index sampling techniques, and diversification, liquidity, and cost management considerations to make investment decisions for the Fund.

The Fund invests in U.S. high yield bonds, commonly referred to as “junk bonds,” and other instruments providing high yield bond exposure, including fallen angel bonds (bonds originally issued as investment grade that have since been downgraded to below investment grade), short-dated bonds (bonds with short terms to maturity), exchange-traded funds (“ETFs”), swaps on the credit default swap index (CDX) and other high yield indices, and swaps on ETFs. The Fund also may invest in non-U.S. high yield bonds and other instruments providing non-U.S. high yield bond exposure.

In addition to the bonds and derivative instruments indicated above, the Fund may (but is not obligated to) invest in a wide variety of exchange-traded and over-the-counter (OTC) derivatives for investment exposure or hedging purposes, including, without limitation, reverse repurchase agreements, options, futures, swap contracts, swaptions, and foreign currency derivative transactions. The Fund may lend its portfolio securities. The Fund is not limited in its use of derivatives or in the total notional value of its derivative positions. Leverage is not a principal component of the Fund’s investment strategy. However, because of its derivative positions, the Fund may at times have gross investment exposure in excess of its net assets (i.e. the Fund may be leveraged), and therefore may be subject to heightened risk of loss during those times. The Fund’s performance can depend substantially on the performance of assets or indices underlying its derivatives even though it does not own those assets or indices.

For collateral and cash management purposes, the Fund may invest in cash equivalents (e.g., Treasury bills, Treasury floating rate notes and Federal Home Loan Bank discount notes and other agency notes), money market instruments, other fixed income securities (including non-U.S. fixed income securities) and instruments (including corporate notes, convertible debt securities and preferred securities) and derivatives they underlie, as well as other investment companies (including ETFs, unit investment trusts, and closed-end funds) that invest primarily in high yield debt investments.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through derivatives and ETFs) at least 80% of its assets in high yield bonds (see “Name Policy”). The term “bond” includes (i) obligations of an issuer to make payments on future dates of principal, interest (whether fixed or variable) or both and (ii) synthetic debt instruments created by GMO by using derivatives. “High yield bonds” generally include those bonds rated BB+ and lower by S&P Global Ratings or Ba1 and lower by Moody’s Investors Service, Inc. They also may include unrated bonds that GMO determines are of similar quality to those with such ratings.

The Fund also may invest in U.S. Treasury Fund, in money market funds unaffiliated with GMO, directly in the types of investments typically held by money market funds, and in fixed income securities issued by non-U.S. developed countries and their agencies and instrumentalities.
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. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in any underlying funds in which it invests. 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, including those risks to which the Fund is exposed as a result of its investments in any underlying funds, see “Additional Information about the Funds’ Investment Strategies, Risks, and Expenses” and “Description of Principal Risks.”

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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 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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Market Risk – Fixed Income – The market price of a fixed income investment can decline due to market-related factors, including rising interest rates and widening credit spreads, or decreased liquidity due, for example, to market uncertainty about the value of a fixed income investment (or class of fixed income investments).

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Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income investment or the obligors of obligations underlying an asset-backed security will be unable or unwilling to satisfy their obligations to pay principal and interest or otherwise to honor their obligations in a timely manner. The market price of a fixed income investment will normally decline as a result of the issuer’s, guarantor’s, or obligors’ failure to meet their payment obligations or in anticipation of such failure. Below investment grade investments have speculative characteristics, and negative changes in economic conditions or other circumstances are more likely to impair the ability of issuers of those investments to make principal and interest payments than issuers of investment grade investments. Investments in distressed or defaulted or other low quality debt investments generally are considered speculative and may involve substantial risks not normally associated with investments in higher quality securities, including adverse business, financial or economic conditions that lead to payment defaults and insolvency proceedings on the part of their issuers. In particular, distressed or defaulted obligations might be repaid, if at all, only after lengthy workout or bankruptcy proceedings, during which the issuer might not make any interest or other payments, and the Fund may incur additional expenses to seek recovery. If GMO’s assessment of the eventual recovery value of a distressed or defaulted debt investment proves incorrect, the Fund may lose a substantial portion or all of its investment or may be required to accept cash or instruments worth less than its original investment.

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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.

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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.

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Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in any underlying funds (including ETFs) in which it invests, including the risk that those underlying funds will not perform as expected. Because the Fund bears the fees and expenses of the underlying funds in which it invests, the increase in fees and expenses of an underlying fund or a reallocation of the Fund’s investments to underlying funds with higher fees or expenses will increase the Fund’s total expenses.

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Focused Investment Risk – Investments focused in asset classes, countries, regions, sectors, industries, currencies, or issuers 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.

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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.

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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.

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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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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.

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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.

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Futures Contracts Risk – The risk of loss to the Fund resulting from its use of futures contracts is potentially unlimited. Futures markets are highly volatile, and the use of futures contracts increases the volatility of the Fund’s net asset value. A liquid secondary market may not exist for any particular futures contract at any particular time, and the Fund might be unable to effect closing transactions to terminate its exposure to the contract. When the Fund uses futures contracts for hedging purposes, it runs the risk that changes in the prices of the contracts will not correlate perfectly with changes in the securities, index, or other asset underlying the contracts or movements in the prices of the Fund’s investments that are the subject of the hedge. In addition, the Fund may be unable to recover or may be delayed in recovering margin or other amounts deposited with a futures commission merchant or futures clearinghouse. Foreign futures contracts are often less liquid and more volatile than U.S. contracts.
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 the Fund’s benchmark (which is 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 VI shares. Class R6 and Class I shares would have substantially similar annual returns to Class VI shares because they invest in the same portfolio of securities. Their annual returns would differ from Class VI shares to the extent that they bear different expenses. Class R6 and Class I shares bear higher expenses than Class VI 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 VI 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 the Fund’s benchmark (which is 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 VI Shares Years Ending December 31
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Quarter: 7.28% (1Q2019)
Lowest Quarter: 1.14% (3Q2019)
Year-to-Date (as of 3/31/20): -11.21%
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 (11.21%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 7.28%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2019
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 1.14%
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, but are net of withholding tax on dividend reinvestments)
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 VI shares only; after-tax returns for other classes will vary.
GMO High Yield Fund | Markit iBoxx USD Liquid High Yield Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes, but are net of withholding tax on dividend reinvestments)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 14.65%
5 Years rr_AverageAnnualReturnYear05
10 Years rr_AverageAnnualReturnYear10
Since Inception rr_AverageAnnualReturnSinceInception 7.77%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 25, 2018
GMO High Yield Fund | Class III  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.50% [1]
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.65%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets none [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.65%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 66
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 208
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 362
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 810
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 66
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 208
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 362
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 810
GMO High Yield Fund | Class IV  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.45% [1]
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.60%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets none [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.60%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 61
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 192
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 335
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 750
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 61
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 192
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 335
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 750
GMO High Yield Fund | Class V  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.435% [1]
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.59%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets none [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.59%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 60
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 189
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 329
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 738
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 60
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 189
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 329
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 738
GMO High Yield Fund | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.405% [1]
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.56%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets none [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.56%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 57
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 179
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 313
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 701
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 57
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 179
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 313
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 701
Annual Return 2019 rr_AnnualReturn2019 14.33%
1 Year rr_AverageAnnualReturnYear01 14.33%
5 Years rr_AverageAnnualReturnYear05
10 Years rr_AverageAnnualReturnYear10
Since Inception rr_AverageAnnualReturnSinceInception 8.73%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 25, 2018
GMO High Yield Fund | Class VI | Return After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 10.91%
5 Years rr_AverageAnnualReturnYear05
10 Years rr_AverageAnnualReturnYear10
Since Inception rr_AverageAnnualReturnSinceInception 5.48%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 25, 2018
GMO High Yield Fund | Class VI | Return After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.46%
5 Years rr_AverageAnnualReturnYear05
10 Years rr_AverageAnnualReturnYear10
Since Inception rr_AverageAnnualReturnSinceInception 5.27%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 25, 2018
GMO High Yield Fund | Class R6  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.50% [1]
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.65%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets none [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.65%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 66
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 208
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 362
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 810
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 66
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 208
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 362
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 810
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 High Yield Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.50% [1]
Other expenses rr_OtherExpensesOverAssets 0.24% [2],[3]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.75%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets none [1],[3]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 77
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 240
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 417
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 930
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 77
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 240
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 417
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 930
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 0.35% 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 portion of its "Specified Operating Expenses" (as defined below) that exceeds 0.10% of the Fund's average daily net assets. "Specified Operating Expenses" means only 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, organizational and start-up expenses, federal securities law filing expenses, printing expenses, state and federal registration fees and custody expenses. GMO is permitted to recover from the Fund, on a class-by-class basis, "Specified Operating Expenses" it has borne or reimbursed (whether through reduction of its fees or otherwise) to the extent that the Fund's "Specified Operating Expenses" later fall below the annualized rate of 0.10% per year or the lower expense limit in effect when GMO seeks to recover the expenses. The Fund, however, is not obligated to pay any such amount more than three years after GMO bore or reimbursed an expense. Any such recovery will not cause the Fund to exceed the annual limitation rate set forth above or the lower expense limit as is in effect at the time GMO seeks to recover 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] The amount includes interest expense incurred by the Fund as a result of entering into reverse repurchase agreements and/or margin on cleared swap contracts, if any. "Other expenses" (before addition of interest expense) and interest expense were approximately 0.11% and 0.03%, respectively.
[3] 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.