Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	GMO TRUST
Prospectus Date	rr_ProspectusDate	Jun. 30, 2016
GMO Alpha Only Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	GMO ALPHA ONLY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Total return greater than that of its benchmark, the Citigroup 3-Month Treasury Bill 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	June 30, 2017
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 29, 2016, the Fund’s portfolio turnover rate (excluding short-term investments) was 85% 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, 2016, excluding transactions in U.S. Treasury Fund, was 31% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	85.00%
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	GMO pursues investment strategies for the Fund that are intended to complement the strategies it is pursuing in other funds or accounts managed by GMO. Accordingly, the Fund is not a standalone investment. The Fund's investment program involves having both long and short investment exposures. GMO seeks to construct a portfolio in which the Fund has long investment exposure to asset classes and sub-asset classes that GMO expects will outperform relative to the asset classes and sub-asset classes to which the Fund has short investment exposure. To gain long investment exposure, the Fund invests directly in securities and may invest in other GMO Funds (collectively, the "underlying GMO Funds"). To gain short investment exposure, the Fund typically invests in over-the-counter (OTC) and exchange-traded derivatives (including futures, swaps and currency forwards) and sells securities short, including short sales of securities the Fund does not own. 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. 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 long and short positions. An important component of those forecasts is GMO's expectation that valuations ultimately revert to their fundamental fair (or intrinsic) value. GMO changes the Fund's holdings 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. If the Fund's long and short positions are effective, the Fund's performance should have a low correlation to the performance of U.S. and non-U.S. equity markets. The factors GMO considers and investment methods GMO uses can change over time. The Fund may invest in securities of any credit quality (including below investment grade securities (commonly referred to as "junk bonds")). The Fund may invest in securities of companies of any market capitalization. In seeking to achieve the Fund's investment objective, GMO may invest a significant portion of the Fund's net assets in cash and cash equivalents. GMO would not consider such investments to be "temporary defensive positions." The Fund also may invest in U.S. Treasury Fund, in money market funds unaffiliated with GMO, or 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. 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 underlying funds (including underlying GMO Funds). The Fund and 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 the Fund or those underlying funds may affect the Fund’s or an underlying fund’s performance more than if the Fund or the underlying 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 the underlying funds, see “Description of Principal Risks.” 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. Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results. GMO often uses quantitative models as part of its investment process. GMO’s models are not necessarily predictive of future market events and use simplifying assumptions that can limit their effectiveness. In addition, the data on which the models are based is subject to limitations (e.g., inaccuracies, staleness) that could adversely affect the Fund’s performance. The Fund also runs the risk that GMO’s assessment of an investment (including a company’s fundamental fair (or intrinsic) value) 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. 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 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 or an underlying 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 or 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. In addition, the value of the Fund’s shares will be adversely affected if the equities that are the subject of the Fund’s short positions appreciate in value. Leveraging Risk – The use of reverse repurchase agreements and other derivatives creates leverage. The Fund and some underlying funds are not limited in their use of derivatives or in the total notional value of their derivative positions. Leverage increases the Fund’s losses when the value of its investments (including derivatives) declines. 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. 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. 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. 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 securities (commonly referred to as “junk bonds”) 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. Small 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. 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. 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. 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. 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). Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying funds (including underlying GMO Funds) in which it invests, including the risk that those underlying funds will not perform as expected or that the Fund will invest in underlying funds with higher fees or expenses.
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 and 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 the Fund or those underlying funds may affect the Fund’s or an underlying fund’s performance more than if the Fund or the underlying 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. 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: 5.32% (4Q2008) Lowest Quarter: – 4.81% (2Q2009) Year-to-Date (as of 3/31/16): 2.49%
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns Periods Ending December 31, 2015
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 Alpha Only Fund | Class III
Risk/Return:	rr_RiskReturnAbstract
Management fee	rr_ManagementFeesOverAssets	0.50%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.15%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.07%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.72%
Expense reimbursement/waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[1]
Total annual fund operating expenses	rr_NetExpensesOverAssets	0.66%	[2]
1 Year	rr_ExpenseExampleYear01	$ 67
3 Years	rr_ExpenseExampleYear03	224
5 Years	rr_ExpenseExampleYear05	395
10 Years	rr_ExpenseExampleYear10	889
1 Year	rr_ExpenseExampleNoRedemptionYear01	67
3 Years	rr_ExpenseExampleNoRedemptionYear03	224
5 Years	rr_ExpenseExampleNoRedemptionYear05	395
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 889
2006	rr_AnnualReturn2006	3.34%
2007	rr_AnnualReturn2007	7.60%
2008	rr_AnnualReturn2008	12.08%
2009	rr_AnnualReturn2009	(7.93%)
2010	rr_AnnualReturn2010	(4.02%)
2011	rr_AnnualReturn2011	4.73%
2012	rr_AnnualReturn2012	(1.21%)
2013	rr_AnnualReturn2013	(1.43%)
2014	rr_AnnualReturn2014	(2.87%)
2015	rr_AnnualReturn2015	(1.27%)
Year to Date Return, Label	rr_YearToDateReturnLabel	Year-to-Date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2016
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	2.49%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Highest Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.32%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Lowest Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.81%)
1 Year	rr_AverageAnnualReturnYear01	(1.27%)
5 Years	rr_AverageAnnualReturnYear05	(0.44%)
10 Years	rr_AverageAnnualReturnYear10	0.74%
Incept.	rr_AverageAnnualReturnSinceInception	3.09%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 29, 1994
GMO Alpha Only Fund | Class IV
Risk/Return:	rr_RiskReturnAbstract
Management fee	rr_ManagementFeesOverAssets	0.50%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.10%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.06%
Total annual fund operating expenses	rr_ExpensesOverAssets	0.66%
Expense reimbursement/waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[1]
Total annual fund operating expenses	rr_NetExpensesOverAssets	0.60%	[2]
1 Year	rr_ExpenseExampleYear01	$ 61
3 Years	rr_ExpenseExampleYear03	205
5 Years	rr_ExpenseExampleYear05	362
10 Years	rr_ExpenseExampleYear10	817
1 Year	rr_ExpenseExampleNoRedemptionYear01	61
3 Years	rr_ExpenseExampleNoRedemptionYear03	205
5 Years	rr_ExpenseExampleNoRedemptionYear05	362
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 817
1 Year	rr_AverageAnnualReturnYear01	(1.19%)
5 Years	rr_AverageAnnualReturnYear05	(0.39%)
10 Years	rr_AverageAnnualReturnYear10
Incept.	rr_AverageAnnualReturnSinceInception	0.68%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 02, 2006
GMO Alpha Only Fund | Return After Taxes on Distributions | Class III
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(2.36%)
5 Years	rr_AverageAnnualReturnYear05	(0.76%)
10 Years	rr_AverageAnnualReturnYear10	(1.56%)
Incept.	rr_AverageAnnualReturnSinceInception	1.08%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 29, 1994
GMO Alpha Only Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class III
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(0.17%)
5 Years	rr_AverageAnnualReturnYear05	(0.30%)
10 Years	rr_AverageAnnualReturnYear10	0.41%
Incept.	rr_AverageAnnualReturnSinceInception	1.95%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 29, 1994
GMO Alpha Only Fund | Citigroup 3-Month Treasury Bill Index (reflects no deduction for fees, expenses, or taxes) | Class III
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.03%
5 Years	rr_AverageAnnualReturnYear05	0.05%
10 Years	rr_AverageAnnualReturnYear10	1.17%
Incept.	rr_AverageAnnualReturnSinceInception	2.64%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 29, 1994
GMO Alpha Only Fund | Citigroup 3-Month Treasury Bill Index (reflects no deduction for fees, expenses, or taxes) | Class IV
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	0.03%
5 Years	rr_AverageAnnualReturnYear05	0.05%
10 Years	rr_AverageAnnualReturnYear10
Incept.	rr_AverageAnnualReturnSinceInception	1.12%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 02, 2006

[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. This reimbursement and waiver will continue through at least June 30, 2017, and may not be terminated prior to this date without the action or consent of the Fund's Board of Trustees.

[2] after expense reimbursement/waiver