XML 79 R167.htm IDEA: XBRL DOCUMENT v3.19.2
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName GMO TRUST
Prospectus Date rr_ProspectusDate Jun. 30, 2019
GMO SGM Major Markets Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading GMO SGM MAJOR MARKETS FUND
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Long-term total return.
Expense [Heading] rr_ExpenseHeading Fees and expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The table below describes the fees and expenses that you may bear for each class of shares if you buy and hold shares of the Fund.
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund operating expenses (expenses that you bear each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination June 30, 2020
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, 2019, the Fund’s portfolio turnover rate (including the accounts of the Fund’s wholly-owned subsidiary, GMO Alternative Asset SPC Ltd., and excluding short-term investments) was 75% 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, 2019 (including the accounts of GMO Alternative Asset SPC Ltd., and excluding transactions in U.S. Treasury Fund and other short-term investments) was 49% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 75.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. The one year amounts shown reflect the expense reimbursement and waiver noted in the expense table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal investment strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund’s benchmark is the FTSE 3-Month Treasury Bill Index. The Fund seeks annualized returns of 5% (gross of fees) above the FTSE 3-Month Treasury Bill Index and annualized volatility (standard deviation) of approximately 6 – 10%, each over a complete market cycle. The Fund does not maintain specified interest rate duration for its portfolio, and its performance is expected to have a low correlation with the performance of major asset classes over a complete market cycle.

The Fund typically takes long and short positions in a range of global equity, bond, currency, and commodity markets using exchange-traded and over-the-counter (OTC) futures, forward non-U.S. exchange contracts, and swaps on commodity indices, as well as making other investments. In constructing the Fund’s portfolio, GMO seeks to take advantage of its proprietary investment models for global tactical asset allocation and market selection.

The Fund normally invests assets not held as margin for futures, forward transactions or swaps in cash directly (e.g., Treasury bills, Treasury floating rate notes, Treasury Separately Traded Registered Interest and Principal Securities (“STRIPS”), Federal Home Loan Bank discount notes, and other agency notes), money market funds unaffiliated with GMO, and shares of U.S. Treasury Fund and directly in the types of investments typically held by money market funds. The Fund also may invest in U.S. and non-U.S. fixed income securities of any credit quality (including below investment grade securities (commonly referred to as “high yield” or “junk bonds”)), maturity or duration.

GMO’s models for this systematic process are based on the following strategies:

•     Value-Based Strategies.   Value factors compare the price of an asset class or market to an economic fundamental value. Generally, value strategies include yield analysis and mean reversion analysis.

•     Sentiment-Based Strategies.   Generally, sentiment-based strategies assess factors such as risk aversion, analyst behavior, and momentum.

In implementing the Fund’s investment strategy, GMO seeks to take risk positions that, in GMO’s view, are proportionate to the return opportunities. As a result, during time periods when GMO believes the return opportunities are high relative to the risks involved, the Fund may take more risk relative to the Fund’s benchmark. Conversely, during time periods when GMO believes the return opportunities are low relative to the risks involved, the Fund may take less risk relative to the Fund’s benchmark.

GMO may eliminate strategies, add new strategies, or cause the Fund to take positions that deviate from GMO’s investment models in response to additional research, changing market conditions, or other factors. The factors GMO considers and investment methods GMO uses can change over time.

The Fund gains exposure to commodities and some other asset classes by investing through a wholly-owned subsidiary advised by GMO, which does not receive any additional management or other fees for its services. The subsidiary invests primarily in commodity-related derivatives (such as over-the-counter swaps on commodity indices) and fixed income investments but also may invest in any other investment in which the Fund is permitted to invest directly. References in this Prospectus to actions taken by the Fund refer to actions taken by the subsidiary as well as the Fund. The Fund does not invest directly in commodities and commodity-related derivatives (such as swaps on commodity indices).

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 on the performance of assets or indices underlying its derivatives even though it does not own those assets or indices. In addition, the Fund may lend its portfolio securities.
Risk [Heading] rr_RiskHeading Principal risks of investing in the Fund
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. An investment in the Fund is subject to different risks, and greater overall risk, than an investment in the components of the Fund’s benchmark. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in its wholly-owned subsidiary and in underlying funds. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were a diversified investment company. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in its wholly-owned subsidiary and in underlying funds, see “Additional Information about the Funds’ Investment Strategies, Risks, and Expenses” and “Description of Principal Risks.”

•   Management and Operational Risk – The Fund runs the risk that GMO’s investment techniques will fail to produce desired results including annualized returns and annualized volatility. In addition, the Fund could produce results consistent with its annualized volatility objective over a complete market cycle yet experience shorter periods of significantly higher or lower volatility. GMO uses quantitative models as part of its investment process and in making investment decisions for the Fund. 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.

•   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.

•   Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

•   Commodities Risk – Commodity prices can be extremely volatile, and exposure to commodities can cause the value of the Fund’s shares to decline or fluctuate in a rapid and unpredictable manner.

•   Futures Contracts Risk – The risk of loss to the Fund resulting from its use of futures contracts is potentially unlimited. Futures markets are highly volatile, and the use of futures contracts may increase the volatility of the Fund’s net asset value. A liquid secondary market may not exist for any particular futures contract at any particular time, and the Fund might be unable to effect closing transactions to terminate its exposure to the contract. When the Fund uses futures contracts for hedging purposes, it runs the risk that changes in the prices of the contracts will not correlate perfectly with changes in the securities, index, or other asset underlying the contracts or movements in the prices of the Fund’s investments that are the subject of the hedge. In addition, the Fund may be unable to reenter or may be delayed in recovering margin or other amounts deposited with a futures commission merchant or futures clearinghouse. Foreign futures contracts are often less liquid and more volatile than U.S. contracts.

•   Market Risk – Fixed Income – The market price of a fixed income investment can decline due to market-related factors, including rising interest rates and widening credit spreads, or decreased liquidity due to market uncertainty about the value of a fixed income investment (or class of fixed income investments).

•   Non-U.S. Investment Risk – The market prices of many non-U.S. securities (particularly of companies tied economically to emerging countries) fluctuate more than those of U.S. securities. Many non-U.S. securities markets (particularly emerging 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.

•   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.

•   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 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.

•   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.

•   Focused Investment Risk – Investments focused in asset classes, countries, regions, sectors, industries, or issuers that are subject to the same or similar risk factors and investments whose prices are closely correlated are subject to greater overall risk than investments that are more diversified or whose prices are not as closely correlated.

•   Counterparty Risk – The Fund runs the risk that the counterparty to a derivatives contract, a clearing member used by the Fund to hold a cleared derivatives contract, or a borrower of the Fund’s securities is unable or unwilling to make timely settlement payments, return the Fund’s margin or otherwise honor its obligations.

•   Market Risk – Asset-Backed Securities – The market price of asset-backed securities, like that of other fixed income investments with complex structures, can decline for a variety of reasons, 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, deal structure, creditworthiness of any credit-support provider, and reliability of various other service providers with access to the payment stream), and a problem in any of these factors can lead to a reduction in the payment stream GMO expected the Fund to receive when the Fund purchased the asset-backed security.

•   Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income investment or obligors of obligations underlying an asset-backed security will be unable or unwilling to satisfy their obligations to pay principal and interest or otherwise to honor their 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 obligors’ failure to meet their payment obligations or in anticipation of such failure. Below investment grade investments have speculative characteristics, and negative changes in economic conditions or other circumstances are more likely to impair the ability of issuers of those investments to make principal and interest payments than issuers of investment grade investments.

•   Illiquidity Risk – Low trading volume, lack of a market maker, large position size, or legal restrictions may limit or prevent the Fund or an underlying fund from selling particular securities or closing derivative positions at desirable prices.

•   Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of its investment in its wholly-owned subsidiary and the underlying funds in which it invests, including the risk that its wholly-owned subsidiary and those underlying funds will not perform as expected. 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.

•   Large Shareholder Risk – To the extent that a large number of shares of the Fund is held by a single shareholder (e.g., an institutional investor or another GMO Fund) or a group of shareholders with a common investment strategy (e.g., GMO asset allocation accounts), the Fund is subject to the risk that a redemption by those shareholders of all or a large portion of their Fund shares will require the Fund to sell securities at disadvantageous prices or otherwise disrupt the Fund’s operations.
Risk Lose Money [Text] rr_RiskLoseMoney Many factors can affect this value, and you may lose money by investing in the Fund.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market price of a particular security held by the Fund may affect the Fund's performance more than if the Fund were a diversified investment company.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and a composite index computed by GMO. As of the date of this Prospectus, there are no Class R6 shares or Class I shares outstanding. The returns information below is for the Fund’s Class III shares. Class R6 and Class I shares would have substantially similar annual returns to Class III shares because they invest in the same portfolio of securities. Their annual returns would differ from Class III shares to the extent that they bear different expenses. While Class R6 shares are expected to bear the same expenses as Class III shares, Class I shares bear higher expenses than Class III shares and therefore would have lower returns. 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 and a composite index computed by GMO.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.gmo.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns/Class III Shares Years Ending December 31
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Quarter: 12.14% (4Q2010) 
Lowest Quarter: -5.74% (3Q2011) 
Year-to-Date (as of 3/31/19): 3.59%
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns Periods Ending December 31, 2018
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 SGM Major Markets Fund | Class III  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 1.00% [1]
Other expenses rr_OtherExpensesOverAssets 0.04%
Total annual fund operating expenses rr_ExpensesOverAssets 1.04%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.04%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 1.00%
1 Year rr_ExpenseExampleYear01 $ 102
3 Years rr_ExpenseExampleYear03 333
5 Years rr_ExpenseExampleYear05 583
10 Years rr_ExpenseExampleYear10 1,299
1 Year rr_ExpenseExampleNoRedemptionYear01 102
3 Years rr_ExpenseExampleNoRedemptionYear03 333
5 Years rr_ExpenseExampleNoRedemptionYear05 583
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,299
2009 rr_AnnualReturn2009 23.95% [2]
2010 rr_AnnualReturn2010 15.63% [2]
2011 rr_AnnualReturn2011 (5.66%) [2]
2012 rr_AnnualReturn2012 (1.00%) [2]
2013 rr_AnnualReturn2013 6.16% [2]
2014 rr_AnnualReturn2014 3.66% [2]
2015 rr_AnnualReturn2015 0.37% [2]
2016 rr_AnnualReturn2016 4.07% [2]
2017 rr_AnnualReturn2017 3.89% [2]
2018 rr_AnnualReturn2018 (2.13%) [2]
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date [2]
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2019 [2]
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.59% [2]
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter: [2]
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2010 [2]
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.14% [2]
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter: [2]
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011 [2]
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.74%) [2]
1 Year rr_AverageAnnualReturnYear01 (2.13%) [2]
5 Years rr_AverageAnnualReturnYear05 1.94% [2]
10 Years rr_AverageAnnualReturnYear10 4.58% [2]
Since Inception rr_AverageAnnualReturnSinceInception 2.46% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2]
GMO SGM Major Markets Fund | Class IV  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.95% [1]
Other expenses rr_OtherExpensesOverAssets 0.04%
Total annual fund operating expenses rr_ExpensesOverAssets 0.99%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.04%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.95%
1 Year rr_ExpenseExampleYear01 $ 97
3 Years rr_ExpenseExampleYear03 318
5 Years rr_ExpenseExampleYear05 556
10 Years rr_ExpenseExampleYear10 1,241
1 Year rr_ExpenseExampleNoRedemptionYear01 97
3 Years rr_ExpenseExampleNoRedemptionYear03 318
5 Years rr_ExpenseExampleNoRedemptionYear05 556
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,241
1 Year rr_AverageAnnualReturnYear01 (2.08%) [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception (0.87%) [2]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 26, 2016 [2]
GMO SGM Major Markets Fund | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.905% [1]
Other expenses rr_OtherExpensesOverAssets 0.04%
Total annual fund operating expenses rr_ExpensesOverAssets 0.95%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.04%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 0.91%
1 Year rr_ExpenseExampleYear01 $ 93
3 Years rr_ExpenseExampleYear03 305
5 Years rr_ExpenseExampleYear05 535
10 Years rr_ExpenseExampleYear10 1,195
1 Year rr_ExpenseExampleNoRedemptionYear01 93
3 Years rr_ExpenseExampleNoRedemptionYear03 305
5 Years rr_ExpenseExampleNoRedemptionYear05 535
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,195
1 Year rr_AverageAnnualReturnYear01 (2.02%) [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.85% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 01, 2015 [2]
GMO SGM Major Markets Fund | Class R6  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 1.00% [1]
Other expenses rr_OtherExpensesOverAssets 0.04%
Total annual fund operating expenses rr_ExpensesOverAssets 1.04%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.04%) [1]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 1.00%
1 Year rr_ExpenseExampleYear01 $ 102
3 Years rr_ExpenseExampleYear03 333
5 Years rr_ExpenseExampleYear05 583
10 Years rr_ExpenseExampleYear10 1,299
1 Year rr_ExpenseExampleNoRedemptionYear01 102
3 Years rr_ExpenseExampleNoRedemptionYear03 333
5 Years rr_ExpenseExampleNoRedemptionYear05 583
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,299
GMO SGM Major Markets Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 1.00% [1]
Other expenses rr_OtherExpensesOverAssets 0.23% [3]
Total annual fund operating expenses rr_ExpensesOverAssets 1.23%
Expense reimbursement/waiver rr_FeeWaiverOrReimbursementOverAssets (0.13%) [1],[3]
Total annual fund operating expenses after expense reimbursement/waiver rr_NetExpensesOverAssets 1.10%
1 Year rr_ExpenseExampleYear01 $ 112
3 Years rr_ExpenseExampleYear03 384
5 Years rr_ExpenseExampleYear05 676
10 Years rr_ExpenseExampleYear10 1,509
1 Year rr_ExpenseExampleNoRedemptionYear01 112
3 Years rr_ExpenseExampleNoRedemptionYear03 384
5 Years rr_ExpenseExampleNoRedemptionYear05 676
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,509
GMO SGM Major Markets Fund | Return After Taxes on Distributions | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (2.28%) [2],[4]
5 Years rr_AverageAnnualReturnYear05 1.23% [2],[4]
10 Years rr_AverageAnnualReturnYear10 4.21% [2],[4]
Since Inception rr_AverageAnnualReturnSinceInception 2.20% [2],[4]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2],[4]
GMO SGM Major Markets Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (1.26%) [2],[4]
5 Years rr_AverageAnnualReturnYear05 1.30% [2],[4]
10 Years rr_AverageAnnualReturnYear10 3.54% [2],[4]
Since Inception rr_AverageAnnualReturnSinceInception 1.86% [2],[4]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2],[4]
GMO SGM Major Markets Fund | FTSE 3-Month Treasury Bill Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class III  
Risk/Return: rr_RiskReturnAbstract  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 1.86% [2]
5 Years rr_AverageAnnualReturnYear05 0.60% [2]
10 Years rr_AverageAnnualReturnYear10 0.35% [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.24% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2]
GMO SGM Major Markets Fund | FTSE 3-Month Treasury Bill 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 1.86% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.27% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 26, 2016 [2]
GMO SGM Major Markets Fund | FTSE 3-Month Treasury Bill Index (Fund benchmark) (reflects no deduction for fees, expenses, or taxes) | Class VI  
Risk/Return: rr_RiskReturnAbstract  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 1.86% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 0.97% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 01, 2015 [2]
GMO SGM Major Markets Fund | FTSE 3-Month Treasury Bill Index +++ (Composite Index) | Class III  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.86% [2]
5 Years rr_AverageAnnualReturnYear05 0.60% [2]
10 Years rr_AverageAnnualReturnYear10 1.47% [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.28% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 11, 2005 [2]
GMO SGM Major Markets Fund | FTSE 3-Month Treasury Bill Index +++ | Class IV  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.86% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 1.27% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 26, 2016 [2]
GMO SGM Major Markets Fund | FTSE 3-Month Treasury Bill Index +++ | Class VI  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.86% [2]
5 Years rr_AverageAnnualReturnYear05 [2]
10 Years rr_AverageAnnualReturnYear10 [2]
Since Inception rr_AverageAnnualReturnSinceInception 0.97% [2]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 01, 2015 [2]
[1] Includes both management fee of 0.85% and class-specific shareholder service fee, if any, for each class of shares. For additional information about the shareholder service fee applicable to each class of shares of the Fund, please see the table included in the section of the Prospectus entitled "Multiple Classes and Eligibility." 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 (excluding, in the case of Class I shares, any amounts paid to financial intermediaries for sub-transfer agency, recordkeeping and other administrative services provided in respect of Class I shareholders), expenses of non-investment related legal services provided to the Fund by or at the direction of GMO, federal securities law filing expenses, printing expenses, state and federal registration fees and custody expenses. GMO also has contractually agreed to waive or reduce the Fund's management fees and shareholder service fees to the extent necessary to offset the management fees and shareholder service fees paid to GMO that are directly or indirectly borne by the Fund or a class of shares of the Fund as a result of the Fund's direct or indirect investments in other series of GMO Trust ("GMO Funds"). Management fees and shareholder service fees will not be waived below zero as a result of this waiver. These reimbursements and waivers will continue through at least June 30, 2020 and may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.
[2] Prior to October 3, 2011, the Fund was managed pursuant to a materially different investment strategy and would have achieved materially different performance results under its current investment strategy from that shown for periods prior to October 3, 2011.
[3] Includes estimate of payments for sub-transfer agency, recordkeeping and other administrative services for Class I's initial fiscal year. GMO has contractually agreed to waive its fees with respect to and/or reimburse Class I shares to the extent that amounts paid by the Fund out of the net assets attributable to Class I shares to financial intermediaries for sub-transfer agency, recordkeeping and other administrative services provided in respect of Class I shareholders exceed 0.10% of the average daily net assets attributable to Class I shares. This reimbursement will continue through at least June 30, 2020 and may not be terminated prior to this date without the action or consent of the Trust's Board of Trustees.
[4] After-tax returns do not reflect distributions made by the Fund for all periods prior to December 1, 2015, the date on which the Fund elected to change its U.S. federal income tax status from that of a partnership to a corporation. Further, as described in "Distributions and Taxes," the Fund elected to be treated and intends to qualify and be treated each year as a regulated investment company under Subchapter M of the Internal Revenue Code of 1986, as amended, for U.S. federal income tax purposes.