Label		Element	Value
Risk/Return:		rr_RiskReturnAbstract
Registrant Name		dei_EntityRegistrantName	GMO TRUST
Prospectus Date		rr_ProspectusDate	Jun. 30, 2015
GMO International Equity Allocation Fund
Risk/Return:		rr_RiskReturnAbstract
Risk/Return [Heading]		rr_RiskReturnHeading	GMO INTERNATIONAL EQUITY ALLOCATION FUND
Objective [Heading]		rr_ObjectiveHeading	Investment objective
Objective, Primary [Text Block]		rr_ObjectivePrimaryTextBlock	Total return greater than that of its benchmark, the MSCI ACWI ex USA.
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 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, 2016
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 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, 2015, the Fund’s portfolio turnover rate (excluding short-term investments) was 18% of the average value of its portfolio.
Portfolio Turnover, Rate		rr_PortfolioTurnoverRate	18.00%
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 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 is a fund of funds and invests primarily in equities traded in non-U.S. markets through shares of the Equity Funds, Alpha Only Fund and Risk Premium Fund (collectively, the "underlying Funds") (see "Additional Information About the Funds' Investment Strategies, Risks, and Expenses — Asset Allocation Funds" and "Investment in Other GMO Funds"). The Fund also may invest directly in securities and derivatives. GMO uses its multi-year forecasts of returns among asset classes, together with its assessment of the relative risks of such asset classes, to determine the Fund's allocations to particular underlying Funds. An important component of those forecasts is the expectation that valuations ultimately revert to their historical mean (average). GMO changes the Fund's holdings of the underlying Funds in response to changes in GMO's investment outlook and market valuations and may use redemptions or purchases of Fund shares to rebalance the Fund's investments. The factors considered and investment methods used by GMO can change over time. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equities (see "Name Policies"). The term "equities" refers to direct and indirect (e.g., through the underlying Funds) investments in common and preferred stocks and other stock-related securities, such as convertible securities, depositary receipts, and exchange-traded equity real estate investment trusts (REITs) and income trusts. The Fund also may invest in U.S. Treasury Fund and in money market funds unaffiliated with GMO.
Risk [Heading]		rr_RiskHeading	Principal risks of investing in the Fund
Risk Narrative [Text Block]		rr_RiskNarrativeTextBlock	The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by those underlying Funds may affect their performance more than if they were diversified investment companies. 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 the underlying Funds, see “Description of Principal Risks.” Market Risk – Equities – The market prices of equities may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equities for less than their value as determined by GMO, the Fund runs the risk that the market prices of these equities will not appreciate or will decline for a variety of reasons, one of which may be GMO’s incorrect assessment of their intrinsic value. An underlying 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. Non-U.S. portfolio transactions generally involve higher commission rates, transfer taxes, and custodial costs than similar transactions in the United States. 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. Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results. GMO often uses quantitative analyses and models as part of its investment process. All models support portfolio decisions but are not necessarily predictive of future market events. These analyses and models also make simplifying assumptions that may limit their effectiveness. In addition, there are limitations (e.g., inaccuracies, staleness) on the data available for analysis or manipulation by the models. Any of those assumptions and/or limitations could adversely affect the Fund’s performance. The Fund also runs the risk that GMO’s assessment of an investment may be 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. Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies. 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. 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 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. In addition, 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 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, a reallocation of the Fund’s investments to underlying Funds with higher fees or expenses will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable than those associated with an investment in funds that charge a fixed management fee. Smaller Company Risk – Smaller companies may have limited product lines, markets, or financial resources, may lack the competitive strength of larger companies, may have inexperienced managers or may 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. Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending creates leverage. Leverage increases the Fund’s losses when the value of its investments (including derivatives) declines. 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 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. Market Risk – Fixed Income Investments – 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). 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. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the ability of issuers of those securities to make principal and interest payments than is the case with issuers of investment grade securities. 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 strongly correlated are subject to greater overall risk than investments that are more diversified. 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 credit worthiness 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. 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), the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its Fund shares will cause the Fund to sell securities at disadvantageous prices or otherwise will 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	Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by those underlying Funds may affect their performance more than if they were diversified investment companies.
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-deferred 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.
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: 21.94% (2Q2009) Lowest Quarter: – 20.16% (3Q2008) Year-to-Date (as of 3/31/15): 3.53%
Performance Table Heading		rr_PerformanceTableHeading	Average Annual Total Returns Periods Ending December 31, 2014
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-deferred arrangements (such as a 401(k) plan or individual retirement account).
GMO International Equity Allocation Fund | Class III
Risk/Return:		rr_RiskReturnAbstract
Purchase premium (as a percentage of amount invested)		rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	0.27%
Redemption fee (as a percentage of amount redeemed)		rr_RedemptionFeeOverRedemption	0.27%
Management fee		rr_ManagementFeesOverAssets	none
Shareholder service fee		rr_DistributionOrSimilarNon12b1FeesOverAssets	none
Other expenses		rr_OtherExpensesOverAssets	0.01%
Acquired fund fees and expenses (underlying fund expenses)	[1]	rr_AcquiredFundFeesAndExpensesOverAssets	0.75%
Total annual operating expenses		rr_ExpensesOverAssets	0.76%
Expense reimbursement	[2]	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)
Total annual operating expenses	[3]	rr_NetExpensesOverAssets	0.75%
1 Year		rr_ExpenseExampleYear01	$ 131
3 Years		rr_ExpenseExampleYear03	307
5 Years		rr_ExpenseExampleYear05	498
10 Years		rr_ExpenseExampleYear10	1,050
1 Year		rr_ExpenseExampleNoRedemptionYear01	103
3 Years		rr_ExpenseExampleNoRedemptionYear03	277
5 Years		rr_ExpenseExampleNoRedemptionYear05	465
10 Years		rr_ExpenseExampleNoRedemptionYear10	$ 1,009
2005		rr_AnnualReturn2005	18.72%
2006		rr_AnnualReturn2006	25.92%
2007		rr_AnnualReturn2007	17.44%
2008		rr_AnnualReturn2008	(41.39%)
2009		rr_AnnualReturn2009	28.07%
2010		rr_AnnualReturn2010	13.03%
2011		rr_AnnualReturn2011	(11.25%)
2012		rr_AnnualReturn2012	17.04%
2013		rr_AnnualReturn2013	16.57%
2014		rr_AnnualReturn2014	(6.22%)
Year to Date Return, Label		rr_YearToDateReturnLabel	Year-to-Date
Bar Chart, Year to Date Return, Date		rr_BarChartYearToDateReturnDate	Mar. 31, 2015
Bar Chart, Year to Date Return		rr_BarChartYearToDateReturn	3.53%
Highest Quarterly Return, Label		rr_HighestQuarterlyReturnLabel	Highest Quarter:
Highest Quarterly Return, Date		rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return		rr_BarChartHighestQuarterlyReturn	21.94%
Lowest Quarterly Return, Label		rr_LowestQuarterlyReturnLabel	Lowest Quarter:
Lowest Quarterly Return, Date		rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return		rr_BarChartLowestQuarterlyReturn	(20.16%)
1 Year		rr_AverageAnnualReturnYear01	(6.72%)
5 Years		rr_AverageAnnualReturnYear05	5.01%
10 Years		rr_AverageAnnualReturnYear10	5.34%
Incept.		rr_AverageAnnualReturnSinceInception	7.40%
Inception Date		rr_AverageAnnualReturnInceptionDate	Oct. 11, 1996
GMO International Equity Allocation Fund | Return After Taxes on Distributions | Class III
Risk/Return:		rr_RiskReturnAbstract
1 Year		rr_AverageAnnualReturnYear01	(7.74%)
5 Years		rr_AverageAnnualReturnYear05	4.31%
10 Years		rr_AverageAnnualReturnYear10	3.73%
Incept.		rr_AverageAnnualReturnSinceInception	5.76%
Inception Date		rr_AverageAnnualReturnInceptionDate	Oct. 11, 1996
GMO International Equity Allocation Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class III
Risk/Return:		rr_RiskReturnAbstract
1 Year		rr_AverageAnnualReturnYear01	(2.37%)
5 Years		rr_AverageAnnualReturnYear05	3.99%
10 Years		rr_AverageAnnualReturnYear10	3.66%
Incept.		rr_AverageAnnualReturnSinceInception	6.01%
Inception Date		rr_AverageAnnualReturnInceptionDate	Oct. 11, 1996
GMO International Equity Allocation Fund | MSCI ACWI ex USA (returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)
Risk/Return:		rr_RiskReturnAbstract
1 Year		rr_AverageAnnualReturnYear01	(3.87%)
5 Years		rr_AverageAnnualReturnYear05	4.43%
10 Years		rr_AverageAnnualReturnYear10	5.13%
Incept.		rr_AverageAnnualReturnSinceInception	5.23%
Inception Date		rr_AverageAnnualReturnInceptionDate	Oct. 11, 1996

[1] These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were approximately 0.67% and 0.08%, respectively.

[2] 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. This reimbursement will continue through at least June 30, 2016, and may not be terminated prior to this date without the action or consent of the Fund's Board of Trustees.

[3] after expense reimbursement (Fund and underlying fund expenses)