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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName GMO TRUST
Prospectus Date rr_ProspectusDate Jun. 30, 2018
GMO Emerging Markets Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading
GMO EMERGING MARKETS FUND
Objective [Heading] rr_ObjectiveHeading
Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.
Expense [Heading] rr_ExpenseHeading
Fees and expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The tables below describe the fees and expenses that you may bear for each class of shares if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption
Shareholder fees
(fees paid directly from your investment)
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, 2019
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, 2018, the Fund’s portfolio turnover rate (excluding short-term investments) was 117% 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, 2018, excluding transactions in U.S. Treasury Fund and other short-term investments, was 87% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 117.00%
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. 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:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption
If you sell your shares
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption
If you do not sell your shares
Strategy [Heading] rr_StrategyHeading
Principal investment strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to emerging markets. "Emerging markets" include all markets that are not treated as "developed markets" in the MSCI World Index or MSCI EAFE Index. The term "equities" refers to direct and indirect investments in common and preferred stocks and other stock-related securities, such as convertible securities, depositary receipts, and equity real estate investment trusts (REITs) and income trusts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging markets (see "Name Policies"). In addition to investing in companies tied economically to emerging markets, the Fund may invest in companies that GMO believes are likely to benefit from growth in the emerging markets. GMO expects that the Fund will have a value bias relative to its benchmark.

GMO uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors, and equity investments based on factors including, but not limited to, valuation, quality and macroeconomic factors. In constructing the Fund's portfolio, GMO considers a number of factors, including the trade-off among forecasted returns, risk relative to the benchmark, transaction costs, and liquidity. GMO also adjusts the Fund's portfolio for factors such as position size, market capitalization, and exposure to particular industries, sectors, countries, regions, or currencies. At times, the Fund may have substantial exposure to a single asset class, industry, sector, country, region, or currency. The Fund may invest in securities of companies of any market capitalization. The factors GMO considers and investment methods GMO uses can change over time.

As an alternative to investing directly in equities, the Fund may invest in exchange-traded and over-the-counter (OTC) derivatives and exchange-traded funds (ETFs). The Fund also may invest in derivatives and ETFs in an attempt to obtain or adjust elements of its long or short investment exposure, and as a substitute for securities lending. Derivatives used may include options, futures, forward currency contracts, warrants, swap contracts, and reverse repurchase agreements. The Fund's foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may overweight and underweight its positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

The Fund also may invest in U.S. Treasury Fund, in money market funds unaffiliated with GMO, and directly in the types of investments typically held by money market funds.
Risk [Heading] rr_RiskHeading
Principal risks of investing in the Fund
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by the Fund may affect the Fund's performance more than if the Fund were a diversified investment company. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see "Additional Information about the Funds' Investment Strategies, Risks, and Expenses" and "Description of Principal Risks."

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

​

•   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, 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) tend to be greater for investments in the securities of 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 of which often are more volatile than the economies of developed countries.

•   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.

​

•   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.

​

•   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.

​

•   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 reduce the value of the Fund's investments.

​

•   Small 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.

​

•   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.

​

•   Focused Investment Risk – Investments focused in a limited number of asset classes, industries, sectors, currencies, countries and regions (or in sectors within a country or region) that are subject to the same or similar risk factors and investments whose prices are closely correlated are subject to greater overall risk than investments that are more diversified or whose prices are not as closely correlated.

​

•   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.

​

•   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 ETFs), 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.

​

•   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 redemption requests.

​

•   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. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. 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 Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads
Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Quarter: 31.90% (2Q2009) 
Lowest Quarter: -30.50% (4Q2008) 
Year-to-Date (as of 3/31/18): 3.05%
Performance Table Heading rr_PerformanceTableHeading
Average Annual Total Returns
Periods Ending December 31, 2017
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads
Returns in the table reflect current purchase premiums and redemption fees.
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 Emerging Markets Fund | Class II  
Risk/Return: rr_RiskReturnAbstract  
Purchase premium (as a percentage of amount invested) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.80%
Redemption fee (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption 0.80% [1]
Management fee rr_ManagementFeesOverAssets 0.75% [2],[3]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.22% [2]
Other expenses rr_OtherExpensesOverAssets 0.10% [4]
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.02% [5]
Total annual fund operating expenses rr_ExpensesOverAssets 1.09%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.13%) [2],[3]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.96%
1 Year rr_ExpenseExampleYear01 $ 260
3 Years rr_ExpenseExampleYear03 500
5 Years rr_ExpenseExampleYear05 760
10 Years rr_ExpenseExampleYear10 1,503
1 Year rr_ExpenseExampleNoRedemptionYear01 177
3 Years rr_ExpenseExampleNoRedemptionYear03 411
5 Years rr_ExpenseExampleNoRedemptionYear05 664
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,386
1 Year rr_AverageAnnualReturnYear01 29.86% [6]
5 Years rr_AverageAnnualReturnYear05 2.21% [6]
10 Years rr_AverageAnnualReturnYear10 (0.11%) [6]
Since Inception rr_AverageAnnualReturnSinceInception 8.19% [6]
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 29, 1996 [6]
GMO Emerging Markets Fund | Class III  
Risk/Return: rr_RiskReturnAbstract  
Purchase premium (as a percentage of amount invested) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.80%
Redemption fee (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption 0.80% [1]
Management fee rr_ManagementFeesOverAssets 0.75% [2],[3]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.15% [2]
Other expenses rr_OtherExpensesOverAssets 0.10% [4]
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.02% [5]
Total annual fund operating expenses rr_ExpensesOverAssets 1.02%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.11%) [2],[3]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.91%
1 Year rr_ExpenseExampleYear01 $ 255
3 Years rr_ExpenseExampleYear03 481
5 Years rr_ExpenseExampleYear05 725
10 Years rr_ExpenseExampleYear10 1,425
1 Year rr_ExpenseExampleNoRedemptionYear01 172
3 Years rr_ExpenseExampleNoRedemptionYear03 391
5 Years rr_ExpenseExampleNoRedemptionYear05 628
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,308
2008 rr_AnnualReturn2008 (55.10%)
2009 rr_AnnualReturn2009 70.59%
2010 rr_AnnualReturn2010 20.51%
2011 rr_AnnualReturn2011 (17.10%)
2012 rr_AnnualReturn2012 16.21%
2013 rr_AnnualReturn2013 (5.86%)
2014 rr_AnnualReturn2014 (6.29%)
2015 rr_AnnualReturn2015 (16.15%)
2016 rr_AnnualReturn2016 16.36%
2017 rr_AnnualReturn2017 32.05%
Year to Date Return, Label rr_YearToDateReturnLabel
Year-to-Date
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2018
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.05%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel
Highest Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 31.90%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel
Lowest Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (30.50%)
1 Year rr_AverageAnnualReturnYear01 29.94%
5 Years rr_AverageAnnualReturnYear05 2.26%
10 Years rr_AverageAnnualReturnYear10 (0.06%)
Since Inception rr_AverageAnnualReturnSinceInception 7.81%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 09, 1993
GMO Emerging Markets Fund | Class IV  
Risk/Return: rr_RiskReturnAbstract  
Purchase premium (as a percentage of amount invested) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.80%
Redemption fee (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption 0.80% [1]
Management fee rr_ManagementFeesOverAssets 0.75% [2],[3]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.105% [2]
Other expenses rr_OtherExpensesOverAssets 0.09% [4]
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.02% [5]
Total annual fund operating expenses rr_ExpensesOverAssets 0.97%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.11%) [2],[3]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.86%
1 Year rr_ExpenseExampleYear01 $ 250
3 Years rr_ExpenseExampleYear03 465
5 Years rr_ExpenseExampleYear05 698
10 Years rr_ExpenseExampleYear10 1,368
1 Year rr_ExpenseExampleNoRedemptionYear01 167
3 Years rr_ExpenseExampleNoRedemptionYear03 376
5 Years rr_ExpenseExampleNoRedemptionYear05 601
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,250
1 Year rr_AverageAnnualReturnYear01 29.98%
5 Years rr_AverageAnnualReturnYear05 2.30%
10 Years rr_AverageAnnualReturnYear10 (0.01%)
Since Inception rr_AverageAnnualReturnSinceInception 9.35%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 09, 1998
GMO Emerging Markets Fund | Class V  
Risk/Return: rr_RiskReturnAbstract  
Purchase premium (as a percentage of amount invested) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.80%
Redemption fee (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption 0.80% [1]
Management fee rr_ManagementFeesOverAssets 0.75% [2],[3]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.085% [2]
Other expenses rr_OtherExpensesOverAssets 0.09% [4]
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.02% [5]
Total annual fund operating expenses rr_ExpensesOverAssets 0.95%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.14%) [2],[3]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.81%
1 Year rr_ExpenseExampleYear01 $ 245
3 Years rr_ExpenseExampleYear03 456
5 Years rr_ExpenseExampleYear05 685
10 Years rr_ExpenseExampleYear10 1,343
1 Year rr_ExpenseExampleNoRedemptionYear01 162
3 Years rr_ExpenseExampleNoRedemptionYear03 366
5 Years rr_ExpenseExampleNoRedemptionYear05 588
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,224
1 Year rr_AverageAnnualReturnYear01 30.02% [7]
5 Years rr_AverageAnnualReturnYear05 2.34% [7]
10 Years rr_AverageAnnualReturnYear10 0.03% [7]
Since Inception rr_AverageAnnualReturnSinceInception 10.75% [7]
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 04, 2003 [7]
GMO Emerging Markets Fund | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Purchase premium (as a percentage of amount invested) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 0.80%
Redemption fee (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption 0.80%
Management fee rr_ManagementFeesOverAssets 0.75% [2],[3]
Shareholder service fee rr_DistributionOrSimilarNon12b1FeesOverAssets 0.055% [2]
Other expenses rr_OtherExpensesOverAssets 0.09% [4]
Acquired fund fees and expenses (underlying fund expenses) rr_AcquiredFundFeesAndExpensesOverAssets 0.02% [5]
Total annual fund operating expenses rr_ExpensesOverAssets 0.92%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.14%) [2],[3]
Total annual fund operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses) rr_NetExpensesOverAssets 0.78%
1 Year rr_ExpenseExampleYear01 $ 242
3 Years rr_ExpenseExampleYear03 447
5 Years rr_ExpenseExampleYear05 669
10 Years rr_ExpenseExampleYear10 1,308
1 Year rr_ExpenseExampleNoRedemptionYear01 159
3 Years rr_ExpenseExampleNoRedemptionYear03 357
5 Years rr_ExpenseExampleNoRedemptionYear05 572
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,190
1 Year rr_AverageAnnualReturnYear01 30.12%
5 Years rr_AverageAnnualReturnYear05 2.38%
10 Years rr_AverageAnnualReturnYear10 0.06%
Since Inception rr_AverageAnnualReturnSinceInception 11.01%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2003
GMO Emerging Markets Fund | Return After Taxes on Distributions | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 29.35%
5 Years rr_AverageAnnualReturnYear05 1.78%
10 Years rr_AverageAnnualReturnYear10 (0.91%)
Since Inception rr_AverageAnnualReturnSinceInception 6.51%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 09, 1993
GMO Emerging Markets Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 17.78%
5 Years rr_AverageAnnualReturnYear05 1.82%
10 Years rr_AverageAnnualReturnYear10 0.23%
Since Inception rr_AverageAnnualReturnSinceInception 6.66%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 09, 1993
GMO Emerging Markets Fund | S&P/IFCI Composite Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class II  
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 37.89% [6]
5 Years rr_AverageAnnualReturnYear05 5.65% [6]
10 Years rr_AverageAnnualReturnYear10 2.50% [6]
Since Inception rr_AverageAnnualReturnSinceInception 7.85% [6]
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 29, 1996 [6]
GMO Emerging Markets Fund | S&P/IFCI Composite 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 37.89%
5 Years rr_AverageAnnualReturnYear05 5.65%
10 Years rr_AverageAnnualReturnYear10 2.50%
Since Inception rr_AverageAnnualReturnSinceInception 6.74%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 09, 1993
GMO Emerging Markets Fund | S&P/IFCI Composite Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class IV  
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 37.89%
5 Years rr_AverageAnnualReturnYear05 5.65%
10 Years rr_AverageAnnualReturnYear10 2.50%
Since Inception rr_AverageAnnualReturnSinceInception 9.74%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 09, 1998
GMO Emerging Markets Fund | S&P/IFCI Composite Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class V  
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 37.89% [7]
5 Years rr_AverageAnnualReturnYear05 5.65% [7]
10 Years rr_AverageAnnualReturnYear10 2.50% [7]
Since Inception rr_AverageAnnualReturnSinceInception 12.35% [7]
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 04, 2003 [7]
GMO Emerging Markets Fund | S&P/IFCI Composite 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 37.89%
5 Years rr_AverageAnnualReturnYear05 5.65%
10 Years rr_AverageAnnualReturnYear10 2.50%
Since Inception rr_AverageAnnualReturnSinceInception 12.66%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 30, 2003
[1] Applies only to shares acquired on or after June 1, 1995 (including shares acquired by reinvestment of dividends or other distributions). With respect to Class III shares purchased through third-party intermediaries and any shares acquired prior to March 27, 2002, the level of redemption fee charged by the Fund is 0.40%.
[2] 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 and state and federal registration fees. 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. In addition, GMO has contractually agreed to waive the shareholder service fees charged to each class of shares of the Fund to the extent necessary to prevent the shareholder service fees paid by the class from exceeding the following amounts of the class's average daily net assets: 0.20% for Class II shares, 0.15% for Class III shares, 0.10% for Class IV shares, 0.05% for Class V shares, and 0.02% for Class VI shares. These reimbursements and waivers will continue through at least June 30, 2019, and may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.
[3] Grantham, Mayo, Van Otterloo & Co. LLC ("GMO") has contractually agreed to reduce its management fee to 0.65% through June 30, 2019. This reduction may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.
[4] The amount has been restated to reflect current fees.
[5] Consists of approximately 0.01% in underlying fund fees and expenses and 0.01% in commissions paid to brokers by the Fund for executing transactions in unaffiliated underlying funds.
[6] For the period from January 9, 1998 to August 12, 2009, no Class II shares were outstanding. The returns shown in the table for that period are those of Class III shares, which have been adjusted downward to reflect Class II's higher total annual fund operating expenses (Class II's expenses during these periods were calculated by adjusting Class III's actual total annual fund operating expenses during such periods upward by the current differential between "Total annual fund operating expenses" for Class II and Class III shares shown in the Fund's "Annual Fund operating expenses" table).
[7] For the period from October 26, 2004 to February 11, 2005, no Class V shares were outstanding. The returns shown in the table for that period are those of Class IV shares, which have higher expenses.