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GMO Multi-Sector Fixed Income Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading GMO Multi-Sector Fixed Income Fund (formerly known as “GMO Core Plus Bond Fund”)​
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Total return in excess of that of its benchmark, the Bloomberg Barclays U.S. Aggregate 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 285% 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 215% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 285.00%
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 program has two principal components. One component seeks to achieve a return commensurate with that of the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by making investments that often will not track its benchmark. These investments principally include global interest rate and currency derivatives and indirect (through other GMO Funds and exchange-traded funds (ETFs)) and direct investments in asset-backed, corporate, government and emerging country debt securities. This second component can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding what investments to make in global interest rate and currency markets and the size of those investments, GMO uses a quantitative approach that considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). GMO evaluates the relative attractiveness of particular markets and instruments using various fixed income risk premium measures, which typically include term structure, foreign exchange, volatility, credit, liquidity and other risks. GMO also may consider the relative attractiveness of yield curve and duration positions in these markets. In addition, GMO seeks to identify opportunities arising from unusual market conditions not otherwise identified by its quantitative models and uses various portfolio construction techniques to manage risk.

In making decisions regarding credit investments, GMO seeks to take advantage of its proprietary investment models to opportunistically allocate the Fund’s assets among credit sectors (e.g., investment grade and high yield) and to systematically identify investments within those credit sectors with the best risk/return profiles.

The factors GMO considers and investment methods GMO uses can change over time. In pursuing its investment program, the Fund may make investments in: (i) bonds denominated in various currencies, including non-U.S. and U.S. government bonds and corporate bonds; (ii) shares of Opportunistic Income Fund (to provide exposure to credit (particularly, asset-backed) markets); (iii) shares of Emerging Country Debt Fund (“ECDF”) (to provide exposure to emerging country debt securities); (iv) ETFs; and (v) shares of U.S. Treasury Fund, money market funds unaffiliated with GMO, and the types of investments typically held by money market funds. The Fund may also engage in short sales and invest in derivatives, including without limitation, to-be-announced transactions, futures contracts, currency and interest rate options, currency forwards, repurchase agreements and reverse repurchase agreements, and swap contracts, such as swaps on securities and securities indices, total return swaps, interest rate swaps, and currency swaps, and other types of derivatives.

As a result primarily of its investment in shares of Opportunistic Income Fund and ECDF, the Fund has and expects to continue to have material exposure to U.S. asset-backed and emerging country debt securities that are below investment grade (below investment grade debt investments are sometimes referred to as “high yield” or “junk bonds,” although these terms are not generally used to refer to emerging country debt securities or asset-backed securities).

GMO normally seeks to maintain an annualized tracking error (standard deviation) relative to the Fund’s benchmark of 1-3% over a complete market cycle and an estimated interest rate duration within 2 years of the benchmark’s duration (approximately 6 years as of 5/31/20). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses — Bond Funds — Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). 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 (e.g., a futures contract, swap contract, currency forward, or option).

The Fund may invest in securities of companies of any market capitalization. In addition, 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.
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 – 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.

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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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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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Market Risk – Asset-Backed Securities – The market price of asset-backed securities, like that of other fixed income investments with complex structures, can decline for a variety of reasons, including market uncertainty about their credit quality and the reliability of their payment streams. Payment streams associated with asset-backed securities held by the Fund depend on many factors (e.g., the cash flow generated by the assets backing the securities, deal structure, creditworthiness of any credit-support provider, and reliability of various other service providers with access to the payment stream), and a problem in any of these factors can lead to a reduction in the payment stream GMO expected the Fund to receive when the Fund purchased the asset-backed security.

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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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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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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.

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Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying funds 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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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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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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Focused Investment Risk – Investments focused in countries, regions, sectors, industries, asset classes, or issuers that are subject to the same or similar risk factors and investments whose prices are closely correlated, such as the Fund’s investments in non-U.S. government bonds and asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans, and home equity loans), are subject to greater overall risk than investments that are more diversified or whose prices are not as closely correlated.

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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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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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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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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.
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: 4.42% (1Q2010)
Lowest Quarter: -3.57% (2Q2013)
Year-to-Date (as of 3/31/20): 1.31%
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 1.31%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.42%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.57%)
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 Multi-Sector Fixed Income Fund | Class III  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.40% [1]
Other expenses rr_OtherExpensesOverAssets 0.05%
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.16% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.61%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.16%) [1]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 179
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 324
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 747
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 46
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 179
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 324
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 747
Annual Return 2010 rr_AnnualReturn2010 13.27%
Annual Return 2011 rr_AnnualReturn2011 8.76%
Annual Return 2012 rr_AnnualReturn2012 9.98%
Annual Return 2013 rr_AnnualReturn2013 0.49%
Annual Return 2014 rr_AnnualReturn2014 9.54%
Annual Return 2015 rr_AnnualReturn2015 (1.55%)
Annual Return 2016 rr_AnnualReturn2016 1.37%
Annual Return 2017 rr_AnnualReturn2017 4.45%
Annual Return 2018 rr_AnnualReturn2018 2.11%
Annual Return 2019 rr_AnnualReturn2019 9.64%
1 Year rr_AverageAnnualReturnYear01 9.64%
5 Years rr_AverageAnnualReturnYear05 3.14%
10 Years rr_AverageAnnualReturnYear10 5.70%
Since Inception rr_AverageAnnualReturnSinceInception 5.33%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1997
GMO Multi-Sector Fixed Income Fund | Class III | Return After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 7.26%
5 Years rr_AverageAnnualReturnYear05 1.29%
10 Years rr_AverageAnnualReturnYear10 3.68%
Since Inception rr_AverageAnnualReturnSinceInception 2.82%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1997
GMO Multi-Sector Fixed Income Fund | Class III | Return After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 5.76%
5 Years rr_AverageAnnualReturnYear05 1.56%
10 Years rr_AverageAnnualReturnYear10 3.58%
Since Inception rr_AverageAnnualReturnSinceInception 3.07%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1997
GMO Multi-Sector Fixed Income Fund | Class III | Bloomberg Barclays U.S. Aggregate Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.72%
5 Years rr_AverageAnnualReturnYear05 3.05%
10 Years rr_AverageAnnualReturnYear10 3.75%
Since Inception rr_AverageAnnualReturnSinceInception 5.16%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1997
GMO Multi-Sector Fixed Income Fund | Class IV  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.35% [1]
Other expenses rr_OtherExpensesOverAssets 0.05%
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.16% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.56%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.16%) [1]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.40%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 41
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 163
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 297
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 686
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 41
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 163
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 297
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 686
1 Year rr_AverageAnnualReturnYear01 9.65%
5 Years rr_AverageAnnualReturnYear05 3.22%
10 Years rr_AverageAnnualReturnYear10 5.76%
Since Inception rr_AverageAnnualReturnSinceInception 4.24%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 26, 2005
GMO Multi-Sector Fixed Income Fund | Class IV | Bloomberg Barclays U.S. Aggregate Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.72%
5 Years rr_AverageAnnualReturnYear05 3.05%
10 Years rr_AverageAnnualReturnYear10 3.75%
Since Inception rr_AverageAnnualReturnSinceInception 4.20%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 26, 2005
GMO Multi-Sector Fixed Income Fund | Class R6  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.40% [1]
Other expenses rr_OtherExpensesOverAssets 0.05%
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.16% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.61%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.16%) [1]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 179
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 324
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 747
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 46
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 179
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 324
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 747
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 Multi-Sector Fixed Income Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.40% [1]
Other expenses rr_OtherExpensesOverAssets 0.15% [3]
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.16% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.71%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.16%) [1],[3]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 56
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 211
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 379
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 867
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 56
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 211
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 379
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 867
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 0.25% 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] Consists of approximately 0.15% in underlying fund fees and expenses, less than 0.01% in interest expense incurred by underlying funds, and 0.01% in purchase premiums and redemption fees paid to underlying funds.
[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.