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AMG GW&K Small Cap Core Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading AMG GW&K Small Cap Core Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The investment objective of the AMG GW&K Small Cap Core Fund (the “Fund”) is to provide investors with long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The table below describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
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)
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 (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 22% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 22.00%
Expense Example [Heading] rr_ExpenseExampleHeading Expense Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example will help you compare the cost of investing in the Fund to the cost of investing in other mutual funds. The Example makes certain assumptions. It assumes that you invest $10,000 as an initial investment in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. It also assumes that your investment has a 5% total return each year and the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on the above assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of small-capitalization companies. The Fund primarily invests in common stock and preferred stock of U.S. small-capitalization companies. Small-capitalization companies are those with a market capitalization at the time of purchase of less than $5 billion or otherwise within the range of capitalizations of companies in the Russell 2000® Index, the S&P SmallCap 600 Index, or the Dow Jones U.S. Small-Cap Total Stock Market Index. As of April 30, 2024, the date of the latest reconstitution of the Russell 2000® Index (implemented by the Index June 28, 2024), the range of market capitalizations of the Russell 2000® Index was $150.4 million to $7.1 billion. As of February 28, 2025, the range of market capitalizations of the S&P SmallCap 600 Index was $322.89 million to $9.706 billion. As of February 28, 2025, the range of market capitalizations of the Dow Jones U.S. Small-Cap Total Stock Market Index was $28.42 million to $19.371 billion. These capitalization ranges will change over time. The Fund may continue to hold securities of a portfolio company that subsequently appreciates above the small-capitalization threshold. Because of this, the Fund may have less than 80% of its net assets in equity securities of small-capitalization companies at any given time.
The Fund invests in an unrestricted opportunity set, pursuing what it believes to be quality companies with either growth- or value-oriented characteristics. GW&K Investment Management, LLC, the subadviser to the Fund (“GW&K” or the “Subadviser”), seeks to assemble a portfolio of securities diversified as to companies and industries. The Subadviser generally expects that each economic sector within the Russell 2000® Index will be represented in the Fund’s portfolio. The Subadviser may consider increasing or reducing the Fund’s investment in a particular industry in view of the Fund’s goal of achieving industry diversification.
Risk [Heading] rr_RiskHeading Principal Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information illustrates the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s performance compares to that of (i) a broad-based index and (ii) an additional index reflecting the market segment(s) in which the Fund invests. As always, past performance of the Fund (before and after taxes) is not an indication of how the Fund will perform in the future. Effective October 1, 2016, outstanding Investor Class shares and Institutional Class shares of the Fund were renamed Class N shares and Class I shares, respectively. To obtain updated performance information please visit wealth.amg.com or call 800.548.4539.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information illustrates the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s performance compares to that of (i) a broad-based index and(ii) an additional index reflecting the market segment(s) in which the Fund invests.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The Fund continues to use the Russell 2000® Index as an additional benchmark that reflects the market segment(s) in which the Fund invests.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 800.548.4539
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress wealth.amg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture As always, past performance of the Fund (before and after taxes) is not an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns as of 12/31/24 (Class N)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter: 25.63% (4th Quarter 2020)
Worst Quarter: -27.98% (1st Quarter 2020)
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns as of 12/31/24
Performance Table Market Index Changed rr_PerformanceTableMarketIndexChanged Effective December 31, 2024, the S&P 500® Index was added as a broad measure of market performance in accordance with recent changes to regulatory disclosure requirements. The Fund continues to use the Russell 2000® Index as an additional benchmark that reflects the market segment(s) in which the Fund invests.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual U.S. 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 an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class N shares only, and after-tax returns for  Class I and Class Z shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”). After-tax returns are shown for Class N shares only, and after-tax returns for  Class I and Class Z shares will vary.
AMG GW&K Small Cap Core Fund | Risk Lose Money [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock There is the risk that you may lose money on your investment.
AMG GW&K Small Cap Core Fund | Risk Not Insured Depository Institution [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit or obligation of any bank, is not endorsed or guaranteed by any bank, and is not insured by the Federal Deposit Insurance Corporation (“FDIC”) or any other government agency.
AMG GW&K Small Cap Core Fund | Market Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Market Risk—market prices of investments held by the Fund may fall rapidly or unpredictably due to a variety of factors, including economic or market conditions, or other factors including terrorism, war, natural disasters and the spread of infectious illness or other public health issues, including epidemics or pandemics, or in response to events that affect particular industries or companies. In addition, unexpected political, regulatory, trade and diplomatic events within the United States and abroad may affect investor and consumer confidence and may adversely impact financial markets and the broader economy, perhaps suddenly and to a significant degree.
AMG GW&K Small Cap Core Fund | Small Capitalization Stock Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Small-Capitalization Stock Risk—the stocks of small-capitalization companies often have greater price volatility, lower trading volume, and less liquidity than the stocks of larger, more established companies.
AMG GW&K Small Cap Core Fund | Growth Stock Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Growth Stock Risk—the prices of equity securities of companies that are expected to experience relatively rapid earnings growth, or “growth stocks,” may be more sensitive to market movements because the prices tend to reflect future investor expectations rather than just current profits.
AMG GW&K Small Cap Core Fund | Value Stock Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Value Stock Risk—value stocks may perform differently from the market as a whole and may be undervalued by the market for a long period of time.
AMG GW&K Small Cap Core Fund | Management Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Management Risk—because the Fund is an actively managed investment portfolio, security selection or focus on securities in a particular style, market sector or group of companies may cause the Fund to incur losses or underperform relative to its benchmarks or other funds with a similar investment objective. There can be no guarantee that the Subadviser’s investment techniques and risk analysis will produce the desired result.
AMG GW&K Small Cap Core Fund | Liquidity Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Liquidity Risk—the Fund may not be able to dispose of particular investments, such as illiquid securities, readily at favorable times or prices or the Fund may have to sell them at a loss.
AMG GW&K Small Cap Core Fund | Class N  
Risk/Return: rr_RiskReturnAbstract  
Management Fee rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.35%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.30%
1 Year rr_ExpenseExampleYear01 $ 132
3 Years rr_ExpenseExampleYear03 412
5 Years rr_ExpenseExampleYear05 713
10 Years rr_ExpenseExampleYear10 $ 1,568
2015 rr_AnnualReturn2015 (3.02%)
2016 rr_AnnualReturn2016 17.44%
2017 rr_AnnualReturn2017 20.32%
2018 rr_AnnualReturn2018 (14.08%)
2019 rr_AnnualReturn2019 30.66%
2020 rr_AnnualReturn2020 17.73%
2021 rr_AnnualReturn2021 21.01%
2022 rr_AnnualReturn2022 (16.58%)
2023 rr_AnnualReturn2023 8.02%
2024 rr_AnnualReturn2024 13.57%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.63%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.98%)
1 Year rr_AverageAnnualReturnYear01 13.57%
5 Years rr_AverageAnnualReturnYear05 7.83%
10 Years rr_AverageAnnualReturnYear10 8.41%
Since Inception rr_AverageAnnualReturnSinceInception [1]
AMG GW&K Small Cap Core Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Management Fee rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.95%
1 Year rr_ExpenseExampleYear01 $ 97
3 Years rr_ExpenseExampleYear03 303
5 Years rr_ExpenseExampleYear05 525
10 Years rr_ExpenseExampleYear10 $ 1,166
1 Year rr_AverageAnnualReturnYear01 13.99%
5 Years rr_AverageAnnualReturnYear05 8.21%
10 Years rr_AverageAnnualReturnYear10 8.80%
Since Inception rr_AverageAnnualReturnSinceInception [1]
AMG GW&K Small Cap Core Fund | Class Z  
Risk/Return: rr_RiskReturnAbstract  
Management Fee rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.20%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.90%
1 Year rr_ExpenseExampleYear01 $ 92
3 Years rr_ExpenseExampleYear03 287
5 Years rr_ExpenseExampleYear05 498
10 Years rr_ExpenseExampleYear10 $ 1,108
1 Year rr_AverageAnnualReturnYear01 14.04%
5 Years rr_AverageAnnualReturnYear05 8.26%
10 Years rr_AverageAnnualReturnYear10
Since Inception rr_AverageAnnualReturnSinceInception 8.76% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 24, 2017 [2]
AMG GW&K Small Cap Core Fund | Return After Taxes on Distributions | Class N  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 12.57%
5 Years rr_AverageAnnualReturnYear05 6.96%
10 Years rr_AverageAnnualReturnYear10 7.17%
Since Inception rr_AverageAnnualReturnSinceInception [1]
AMG GW&K Small Cap Core Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class N  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.82%
5 Years rr_AverageAnnualReturnYear05 6.09%
10 Years rr_AverageAnnualReturnYear10 6.54%
Since Inception rr_AverageAnnualReturnSinceInception [1]
AMG GW&K Small Cap Core Fund | S&P 500® Index (reflects no deduction for fees, expenses, or taxes) | Class Z  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 25.02% [2]
5 Years rr_AverageAnnualReturnYear05 14.53% [2]
10 Years rr_AverageAnnualReturnYear10 13.10% [2]
Since Inception rr_AverageAnnualReturnSinceInception 14.25% [1],[2]
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 24, 2017 [2]
AMG GW&K Small Cap Core Fund | Russell 2000® Index (reflects no deduction for fees, expenses, or taxes) | Class Z  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 11.54% [2]
5 Years rr_AverageAnnualReturnYear05 7.40% [2]
10 Years rr_AverageAnnualReturnYear10 7.82% [2]
Since Inception rr_AverageAnnualReturnSinceInception 7.62% [1],[2]
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 24, 2017 [2]
[1] Class Z and Index performance shown reflects performance since the inception date of the Fund's Class Z shares on February 24, 2017.
[2] Effective December 31, 2024, the S&P 500® Index was added as a broad measure of market performance in accordance with recent changes to regulatory disclosure requirements. The Fund continues to use the Russell 2000® Index as an additional benchmark that reflects the market segment(s) in which the Fund invests.