Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	GMO TRUST
Prospectus Date	rr_ProspectusDate	Jun. 30, 2013
GMO Trust | GMO Asset Allocation International Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	GMO ASSET ALLOCATION INTERNATIONAL BOND FUND
Objective [Heading]	rr_ObjectiveHeading	Investment objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Total return in excess of that of its benchmark, the J.P. Morgan GBI Global ex U.S.
Expense [Heading]	rr_ExpenseHeading	Fees and expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The table below describes the fees and expenses that you may pay 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 pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	June 30, 2014
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. Because the Fund had not yet commenced operations as of the date of this Prospectus, the Fund’s portfolio turnover rate is not available.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	The amounts represent an annualized estimate of the Fund’s operating expenses for its initial fiscal year.
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. 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 Manager pursues investment strategies for the Fund that are intended to complement the strategies being pursued by the Manager in other funds or accounts managed by GMO’s Asset Allocation Team. Accordingly, the Fund is not a standalone investment and the Fund’s investment returns may be more volatile than a standalone investment vehicle. The Manager uses multi-year forecasts of returns and risk to determine the Fund’s strategic direction. The factors considered and investment methods used by the Manager can change over time. Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward, or option). The Fund is permitted to invest in bonds of any kind (e.g., bonds of any maturity, duration, or credit quality). While the Fund principally invests in non-U.S. bonds, it may invest in any sector of the bond market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The sectors and types of bonds in which the Fund may invest include, but are not limited to: non-U.S. government securities and other investment grade bonds denominated in various currencies, including bonds issued by the U.S. government, and their agencies or instrumentalities (whether or not guaranteed or insured by those governments), corporations and municipalities (taxable and tax-exempt); below investment grade bonds (commonly referred to as “junk bonds”); inflation indexed bonds issued by non-U.S. governments and the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and their agencies or instrumentalities (whether or not guaranteed or insured by those governments) and inflation indexed bonds issued by corporations; sovereign debt of emerging countries and other bonds issued in emerging countries (including junk bonds); and asset-backed securities, including mortgage related and mortgage-backed securities. The Fund also may invest in exchange-traded and over-the-counter (OTC) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivative positions. As a result of its derivative positions, the Fund will typically have gross investment exposures in excess of its net assets (i.e., the Fund will be 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. The Fund may gain exposure to the investments described above by investing in shares of other GMO Funds, including High Quality Short-Duration Bond Fund (to seek a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and non-U.S. debt investments) and Debt Opportunities Fund (to gain exposure to asset-backed securities). The Fund also may invest in U.S. Treasury Fund and money market funds that are unaffiliated with GMO. The Fund may invest up to 100% of its assets in junk bonds. The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund’s interest rate duration will change depending on the Fund’s investments and the Manager’s assessment of different sectors of the bond market.
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 “Description of Principal Risks.” Market Risk – Fixed Income Investments – The market price of a fixed income investment can decline due to a number of 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). Currency Risk – Fluctuations in exchange rates will adversely affect the market value of the Fund’s non-U.S. currency holdings and investments denominated in non-U.S. currencies. Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results. The Fund’s portfolio managers may use quantitative analyses and models, and any imperfections, errors, or limitations in those analyses and models could affect the ability of the portfolio managers to implement the Fund’s strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and may not include the most recent information about a company or a security. 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. 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 capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities. 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. Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the underlying assets, rates, or indices. Derivatives also present other risks, including market risk, liquidity risk, currency risk, credit risk, and counterparty risk. 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. 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. markets are less stable, smaller, less liquid, and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Non-U.S. portfolio transactions generally involve higher commission rates, transfer taxes, and custodial costs than similar transactions in the U.S. 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 or interest it receives on non-U.S. investments, (ii) transactions in those investments, and (iii) the repatriation of proceeds generated from the sale of those investments. Also, many non-U.S. markets require a license for the Fund to invest directly in those 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. 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 with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. 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 tend to be more volatile than the economies of developed countries. 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 number 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 areas can lead to a reduction in the payment stream the Manager expected the Fund to receive at the time the Fund purchased the asset-backed security. Liquidity 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 unwinding 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 adversely affect the value of the Fund’s investments. Focused Investment Risk – Focusing investments in countries, regions, sectors, companies, or industries with high positive correlations to one another creates more risk than if the Fund’s investments were less correlated. 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. 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 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	Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.
GMO Trust | GMO Asset Allocation International Bond Fund | Class III
Risk/Return:	rr_RiskReturnAbstract
Management fee	rr_ManagementFeesOverAssets	0.25%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.15%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.18%	[2]
Total annual operating expenses	rr_ExpensesOverAssets	0.58%	[2]
Expense reimbursement/waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.18%)	[1],[2]
Total annual operating expenses after expense reimbursement/waiver	rr_NetExpensesOverAssets	0.40%	[2]
1 Year	rr_ExpenseExampleYear01	$ 59
3 Years	rr_ExpenseExampleYear03	186
1 Year	rr_ExpenseExampleNoRedemptionYear01	59
3 Years	rr_ExpenseExampleNoRedemptionYear03	186
GMO Trust | GMO Asset Allocation International Bond Fund | Class VI
Risk/Return:	rr_RiskReturnAbstract
Management fee	rr_ManagementFeesOverAssets	0.25%	[1]
Shareholder service fee	rr_DistributionOrSimilarNon12b1FeesOverAssets	0.055%	[1]
Other expenses	rr_OtherExpensesOverAssets	0.18%	[2]
Total annual operating expenses	rr_ExpensesOverAssets	0.49%	[2]
Expense reimbursement/waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.18%)	[1],[2]
Total annual operating expenses after expense reimbursement/waiver	rr_NetExpensesOverAssets	0.31%	[2]
1 Year	rr_ExpenseExampleYear01	50
3 Years	rr_ExpenseExampleYear03	157
1 Year	rr_ExpenseExampleNoRedemptionYear01	50
3 Years	rr_ExpenseExampleNoRedemptionYear03	$ 157

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "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 the Manager, federal securities law filing expenses, printing expenses, state and federal registration fees and custody expenses. The Manager also has 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 directly or indirectly paid to the Manager as a result of the Fund's direct or indirect investments in other 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, 2014, and may not be terminated prior to this date without the action or consent of the Fund's Board of Trustees.

[2] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.