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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName GMO TRUST
Prospectus Date rr_ProspectusDate Jun. 30, 2017
GMO SGM Major Markets Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
GMO SGM MAJOR MARKETS FUND
Objective [Heading] rr_ObjectiveHeading
Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Long-term 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
June 30, 2018
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, when Fund shares are held in a taxable account, higher 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 28, 2017, the Fund’s portfolio turnover rate (including the accounts of the Fund’s wholly-owned subsidiary, GMO Alternative Asset SPC Ltd., and excluding short-term investments) was 47% 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 28, 2017 (including the accounts of GMO Alternative Asset SPC Ltd., and excluding transactions in U.S. Treasury Fund and other short-term investments) was 15% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 47.00%
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 benchmark is the Citigroup 3-Month Treasury Bill Index. The Fund seeks annualized returns of 5% (gross of fees) above the Citigroup 3-Month Treasury Bill Index and annualized volatility (standard deviation) of approximately 6-10%, each over a complete market cycle. The Fund does not maintain specified interest rate duration for its portfolio, and its performance is expected to have a low correlation with the performance of major asset classes over a complete market cycle.
The Fund typically takes long and short positions in a range of global equity, bond, currency, and commodity markets using exchange-traded futures and forward non-U.S. exchange contracts, as well as making other investments. The Fund seeks to take advantage of GMO's proprietary investment models for global tactical asset allocation and equity, bond, currency, and commodity market selection.
The Fund normally invests assets not held as margin for futures or forward transactions in cash directly (e.g., Treasury bills, Treasury floating rate notes, Treasury Separately Traded Registered Interest and Principal Securities ("STRIPS"), Federal Home Loan Bank discount notes, and other agency notes), money market funds unaffiliated with GMO, or directly in the types of investments typically held by money market funds. The Fund also may invest in U.S. and non-U.S. fixed income securities of any credit quality (including below investment grade securities (commonly referred to as "junk bonds")), maturity or duration and in shares of U.S. Treasury Fund.
GMO's models for this systematic process are based on the following strategies:
•   Value-Based Strategies.   Value factors compare the price of an asset class or market to an economic fundamental value. Generally, value strategies include yield analysis and mean reversion analysis.
​
•   Sentiment-Based Strategies.   Generally, sentiment-based strategies assess factors such as risk aversion, analyst behavior, and momentum.
​
In implementing the Fund's investment strategy, GMO seeks to take risk positions that, in GMO's view, are proportionate to the return opportunities. As a result, during time periods when GMO believes the return opportunities are high relative to the risks involved, the Fund may take more risk relative to the Fund's benchmark. Conversely, during time periods when GMO believes the return opportunities are low relative to the risks involved, the Fund may take less risk (or no risk) relative to the Fund's benchmark.
GMO may eliminate strategies, add new strategies, or cause the Fund to take positions that deviate from GMO's investment models in response to additional research, changing market conditions, or other factors. The factors GMO considers and investment methods GMO uses can change over time.
The Fund gains exposure to commodities and some other asset classes by investing through a wholly-owned subsidiary advised by GMO, which does not receive any additional management or other fees for its services. The subsidiary invests primarily in commodity-related derivatives and fixed income investments but also may invest in any other investment in which the Fund is permitted to invest directly. References in this Prospectus to actions taken by the Fund refer to actions undertaken by the subsidiary as well as the Fund. The Fund does not invest directly in commodities and commodity-related derivatives (such as a swap on a commodity index) but may do so indirectly through its subsidiary (or otherwise).
The Fund is not limited in its use of derivatives or in the total notional value of its derivative positions. As a result of its derivative positions, the Fund typically has gross investment exposures in excess of its net assets (i.e., the Fund typically is leveraged) and therefore is subject to heightened risk of loss. The Fund's performance can depend substantially, if not primarily, 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. An investment in the Fund is subject to different risks, and greater overall risk, than an investment in the components of the Fund's benchmark. References to investments include those held directly by the Fund and indirectly through the Fund's investments in its wholly-owned subsidiary and in underlying funds. 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 its wholly-owned subsidiary and in underlying funds, see "Description of Principal Risks."
•   Management and Operational Risk – The Fund runs the risk that GMO's investment techniques will fail to produce desired results (including the annualized volatility and the annualized returns above the Citigroup 3-Month Treasury Bill Index that the Fund seeks). In addition, the Fund could produce results consistent with annualized volatility over a complete market cycle yet experience shorter periods of significantly higher or lower volatility. GMO uses quantitative models as part of its investment process, and relies heavily on those models in making investment decisions for the Fund. GMO's models may not accurately predict future market events. In addition, they use 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 company'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.
​
•   Market Risk – Equities – The market price of an equity may decline due to factors affecting the issuer, 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 determined 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 of the equity's fundamental fair (or intrinsic) value. 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.
​
•   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.
​
•   Commodities Risk – Commodity prices can be extremely volatile, and exposure to commodities can cause the net asset value of the Fund's shares to decline or fluctuate in a rapid and unpredictable manner.
​
•   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 may increase 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. If the Fund uses futures contracts for hedging purposes, it runs the risk that changes in the prices of the contracts may 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 delayed or prevented from 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.
​
•   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 stemming from the market's uncertainty about the value of a fixed income investment (or class of fixed income investments).
​
•   Non-U.S. Investment Risk – The market prices of many non-U.S. securities fluctuate more than those of U.S. securities. Many non-U.S. securities 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. 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, including 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 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) tend to be greater for investments in companies tied economically to emerging countries, the economies of which may be predominantly based on only a few industries or dependent on revenues from particular commodities and which often are more volatile than the economies of developed countries.
​
•   Market Disruption and Geopolitical Risk – Geopolitical and other events 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 adversely affect the value of the Fund's investments.
​
•   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, rates, or indices. Derivatives also present other risks, including market risk, illiquidity risk, currency risk, credit risk, and counterparty risk. 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 investment, pool of investments, index or currency. 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 reverse repurchase agreements and other derivatives creates leverage. Leverage increases the Fund's losses when the value of its investments (including derivatives) declines.
​
•   Focused Investment Risk – Investments focused in countries, regions, sectors, industries, 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.
​
•   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 will be unable or unwilling to make timely settlement payments, return the Fund's margin or otherwise honor its obligations.
​
•   Market Risk – Asset-Backed Securities – The market price of fixed income investments with complex structures, such as asset-backed securities, can decline due to a variety of factors, 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, the deal structure, the creditworthiness of any credit-support provider, and the reliability of various other service providers with access to the payment stream), and a problem in any one of these factors can lead to a reduction in the payment stream GMO expected the Fund to receive at the time the Fund purchased the asset-backed security.
​
•   Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income investment or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligation to pay principal and interest or otherwise to honor its 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 obligor's failure to meet its payment obligations, or in anticipation of such failure. Below investment grade investments have speculative characteristics, and 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 is the case with issuers of investment grade investments.
​
•   Illiquidity Risk – Low trading volume, lack of a market maker, large position size, or legal restrictions may limit or prevent the Fund or an underlying fund from selling particular securities or closing derivative positions at desirable prices.
​
•   Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of its investment in its wholly-owned subsidiary and the underlying funds in which it invests, including the risk that its wholly-owned subsidiary and those underlying funds will not perform as expected.
​
•   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.
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 and a composite index computed by GMO. 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). 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 and a composite index computed by GMO.
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: 12.14% (4Q2010) 
Lowest Quarter: -22.27% (4Q2008) 
Year-to-Date (as of 3/31/17): 3.09%
Performance Table Heading rr_PerformanceTableHeading
Average Annual Total Returns
Periods Ending December 31, 2016
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
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).
 
GMO SGM Major Markets Fund | Class III  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.85% [1]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.15% [1]
Other expenses rr_OtherExpensesOverAssets 0.04%
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 1.05%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.04%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 1.01%
1 Year rr_ExpenseExampleYear01 $ 103
3 Years rr_ExpenseExampleYear03 343
5 Years rr_ExpenseExampleYear05 602
10 Years rr_ExpenseExampleYear10 1,343
1 Year rr_ExpenseExampleNoRedemptionYear01 103
3 Years rr_ExpenseExampleNoRedemptionYear03 343
5 Years rr_ExpenseExampleNoRedemptionYear05 602
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,343
2007 rr_AnnualReturn2007 8.58% [2]
2008 rr_AnnualReturn2008 (26.28%) [2]
2009 rr_AnnualReturn2009 23.95% [2]
2010 rr_AnnualReturn2010 15.63% [2]
2011 rr_AnnualReturn2011 (5.66%) [2]
2012 rr_AnnualReturn2012 (1.00%) [2]
2013 rr_AnnualReturn2013 6.16% [2]
2014 rr_AnnualReturn2014 3.66% [2]
2015 rr_AnnualReturn2015 0.37% [2]
2016 rr_AnnualReturn2016 4.07% [2]
Year to Date Return, Label rr_YearToDateReturnLabel
Year-to-Date
 [2]
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2017 [2]
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.09% [2]
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel
Highest Quarter:
 [2]
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2010 [2]
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.14% [2]
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel
Lowest Quarter:
 [2]
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008 [2]
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (22.27%) [2]
1 Year rr_AverageAnnualReturnYear01 4.07% [2]
5 Years rr_AverageAnnualReturnYear05 2.62% [2]
10 Years rr_AverageAnnualReturnYear10 2.10% [2]
Since Inception rr_AverageAnnualReturnSinceInception 2.74% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2]
GMO SGM Major Markets Fund | Class IV  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.85% [1]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.10% [1]
Other expenses rr_OtherExpensesOverAssets 0.05%
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 1.01%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.05%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.96%
1 Year rr_ExpenseExampleYear01 $ 98
3 Years rr_ExpenseExampleYear03 329
5 Years rr_ExpenseExampleYear05 579
10 Years rr_ExpenseExampleYear10 1,296
1 Year rr_ExpenseExampleNoRedemptionYear01 98
3 Years rr_ExpenseExampleNoRedemptionYear03 329
5 Years rr_ExpenseExampleNoRedemptionYear05 579
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,296
GMO SGM Major Markets Fund | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.85% [1]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.055% [1]
Other expenses rr_OtherExpensesOverAssets 0.04%
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.96%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.04%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.92%
1 Year rr_ExpenseExampleYear01 $ 94
3 Years rr_ExpenseExampleYear03 315
5 Years rr_ExpenseExampleYear05 554
10 Years rr_ExpenseExampleYear10 1,239
1 Year rr_ExpenseExampleNoRedemptionYear01 94
3 Years rr_ExpenseExampleNoRedemptionYear03 315
5 Years rr_ExpenseExampleNoRedemptionYear05 554
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,239
1 Year rr_AverageAnnualReturnYear01 4.15% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 3.54% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 01, 2015 [2]
GMO SGM Major Markets Fund | Return After Taxes on Distributions | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.58% [2],[3]
5 Years rr_AverageAnnualReturnYear05 2.12% [2],[3]
10 Years rr_AverageAnnualReturnYear10 1.86% [2],[3]
Since Inception rr_AverageAnnualReturnSinceInception 2.53% [2],[3]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2],[3]
GMO SGM Major Markets Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 2.76% [2],[3]
5 Years rr_AverageAnnualReturnYear05 1.84% [2],[3]
10 Years rr_AverageAnnualReturnYear10 1.55% [2],[3]
Since Inception rr_AverageAnnualReturnSinceInception 2.08% [2],[3]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2],[3]
GMO SGM Major Markets Fund | Citigroup 3-Month Treasury Bill Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class III  
Risk/Return: rr_RiskReturnAbstract  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes
(reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 0.27% [2]
5 Years rr_AverageAnnualReturnYear05 0.09% [2]
10 Years rr_AverageAnnualReturnYear10 0.73% [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.22% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2]
GMO SGM Major Markets Fund | Citigroup 3-Month Treasury Bill Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes
(reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 0.27% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 0.26% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 01, 2015 [2]
GMO SGM Major Markets Fund | Citigroup 3-Month Treasury Bill Index +++ (Composite Index) | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.27% [2]
5 Years rr_AverageAnnualReturnYear05 0.09% [2]
10 Years rr_AverageAnnualReturnYear10 0.40% [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.26% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2]
GMO SGM Major Markets Fund | Citigroup 3-Month Treasury Bill Index +++ (Composite Index) | Class VI  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.27% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 0.26% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 01, 2015 [2]
[1] 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, 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 as a result of this waiver. These reimbursements and waivers will continue through at least June 30, 2018, and may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.
[2] Prior to October 3, 2011, the Fund was managed pursuant to a materially different investment strategy and would have achieved materially different performance results under its current investment strategy from that shown for periods prior to October 3, 2011.
[3] After-tax returns do not reflect distributions made by the Fund for all periods prior to December 1, 2015, the date on which the Fund elected to change its U.S. federal income tax status from that of a partnership to a corporation. Further, as described in "Distributions and Taxes," the Fund elected to be treated and intends to qualify and be treated each year as a regulated investment company under Subchapter M of the Internal Revenue Code of 1986, as amended, for U.S. federal income tax purposes.