S000009909 [Member] Investment Risks - AMG River Road Large Cap Value Select Fund	Oct. 31, 2025
Focused Investment Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Focused Investment Risk—to the extent the Fund invests a substantial portion of its assets in a relatively small number of securities or a particular market, industry, group of industries, country, region, group of countries, asset class or sector, it generally will be subject to greater risk than a fund that invests in a more diverse investment portfolio. In addition, the value of the Fund would be more susceptible to any single economic, market, political or regulatory occurrence affecting, for example, that particular market, industry, region or sector.
Large Capitalization Stock Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Large-Capitalization Stock Risk—the stocks of large-capitalization companies are generally more mature and may not be able to reach the same levels of growth as the stocks of small- or mid-capitalization companies.
Management Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	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.
Convertible Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Convertible Securities Risk— convertible preferred stocks, which are convertible into shares of the issuer’s common stock and pay regular dividends, and convertible debt securities, which are convertible into shares of the issuer’s common stock and bear interest, are subject to the risks of equity securities and fixed income securities. The lower the conversion premium, the more likely the price of the convertible security will follow the price of the underlying common stock. Conversely, higher premium convertible securities are more likely to exhibit the behavior of bonds because the likelihood of conversion is lower, which may cause their prices to fall as interest rates rise. There is the risk that the issuer of convertible preferred stock will not be able to make dividend payments or that the issuer of a convertible bond will not be able to make principal and/or interest payments.
Currency Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Currency Risk—fluctuations in exchange rates may affect the total loss or gain on a non-U.S. dollar investment when converted back to U.S. dollars and exposure to non-U.S. currencies may subject the Fund to the risk that those currencies will decline in value relative to the U.S. dollar.
Foreign Investment Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Foreign Investment Risk—investments in foreign issuers involve additional risks (such as risks arising from less frequent trading, changes in political or social conditions, and less publicly available information about non-U.S. issuers) that differ from those associated with investments in U.S. issuers and may result in greater price volatility.
High Portfolio Turnover Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	High Portfolio Turnover Risk—higher portfolio turnover may adversely affect Fund performance by increasing Fund transaction costs and may increase a shareholder’s tax liability.
Master Limited Partnership Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Master Limited Partnership Risk—investments in master limited partnerships are subject to similar risks to those associated with the specific industry or industries in which the partnership invests, such as the risk of investing in the real estate or oil and gas industries. In addition, investments in master limited partnerships are subject to the risks of investing in a partnership, including limited control and voting rights on matters affecting the partnership and fewer investor protections compared to corporations.
PTP Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	PTP Risk— investing in PTPs (including master limited partnerships) involves special risks in addition to those typically associated with publicly traded companies. PTPs are exposed to the risks of their underlying assets, which in many cases includes the same types of risks as energy and natural resources companies, such as commodity pricing risk, supply and demand risk and depletion and exploration risk. PTPs are also subject to capital markets risk, which is the risk that they may be unable to raise capital to execute their growth strategies. PTPs are also subject to tax risk, which is the risk that PTPs may lose their partnership status for tax purposes. The Fund’s ability to make investments in certain PTPs, including master limited partnerships, can be limited by the Fund’s intention to qualify as a regulated investment company accorded favorable tax treatment under the Internal Revenue Code, and if the Fund does not appropriately limit such investments or if such investments are recharacterized for U.S. federal income tax purposes, the Fund’s status as a regulated investment company may be jeopardized.
Real Estate Industry Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Real Estate Industry Risk—investments in the Fund may be subject to many of the same risks as a direct investment in real estate. The stock prices of companies in the real estate industry, including REITs, are typically sensitive to changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use, and rents, as well as the management skill and creditworthiness of the issuer. Investments in the real estate sector also may be adversely impacted by natural or environmental disasters. REITs also depend generally on their ability to generate cash flow to make distributions to shareholders or unitholders and are subject to the risk of failing to qualify for favorable tax treatment under the Internal Revenue Code.
Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Sector Risk—issuers and companies that are in similar industry sectors may be similarly affected by particular economic or market events; to the extent the Fund has substantial holdings within a particular sector, the risks associated with that sector increase. Stocks in the financials sector may comprise a significant portion of the Fund's portfolio. Unique risks of the financials sector include, but are not limited to, government regulation uncertainty, yield curve fluctuation, asset flow fluctuation, and capital market fluctuations.
Value Stock Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	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.
Market Risks [Member]
Prospectus [Line Items]
Risk [Text Block]	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.
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	There is the risk that you may lose money on your investment.
Risk Not Insured Depository Institution [Member]
Prospectus [Line Items]
Risk [Text Block]	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.
Risk Nondiversified Status [Member]
Prospectus [Line Items]
Risk [Text Block]	Non-Diversified Fund Risk—the Fund is non-diversified and therefore a greater percentage of holdings may be focused in a small number of issuers or a single issuer, which can place the Fund at greater risk. Notwithstanding the Fund’s status as a “non-diversified” investment company under the Investment Company Act of 1940 (the “1940 Act”), the Fund intends to qualify each year as a regulated investment company accorded favorable tax treatment under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”), which imposes its own diversification requirements that are less restrictive than the requirements applicable to “diversified” investment companies under the 1940 Act. The Fund’s intention to qualify as a regulated investment company may limit its pursuit of its investment strategy and its investment strategy could limit its ability to so qualify.

S000009909 [Member] Investment Risks - AMG River Road Large Cap Value Select Fund

Oct. 31, 2025

Focused Investment Risk—to the extent the Fund invests a substantial portion of its assets in a relatively small number of securities or a particular market, industry, group of industries, country, region, group of countries, asset class or sector, it generally will be subject to greater risk than a fund that invests in a more diverse investment portfolio. In addition, the value of the Fund would be more susceptible to any single economic, market, political or regulatory occurrence affecting, for example, that particular market, industry, region or sector.

Large Capitalization Stock Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Large-Capitalization Stock Risk—the stocks of large-capitalization companies are generally more mature and may not be able to reach the same levels of growth as the stocks of small- or mid-capitalization companies.

Management Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

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.

Convertible Securities Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Convertible Securities Risk— convertible preferred stocks, which are convertible into shares of the issuer’s common stock and pay regular dividends, and convertible debt securities, which are convertible into shares of the issuer’s common stock and bear interest, are subject to the risks of equity securities and fixed income securities. The lower the conversion premium, the more likely the price of the convertible security will follow the price of the underlying common stock. Conversely, higher premium convertible securities are more likely to exhibit the behavior of bonds because the likelihood of conversion is lower, which may cause their prices to fall as interest rates rise. There is the risk that the issuer of convertible preferred stock will not be able to make dividend payments or that the issuer of a convertible bond will not be able to make principal and/or interest payments.

Currency Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Currency Risk—fluctuations in exchange rates may affect the total loss or gain on a non-U.S. dollar investment when converted back to U.S. dollars and exposure to non-U.S. currencies may subject the Fund to the risk that those currencies will decline in value relative to the U.S. dollar.

Foreign Investment Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Foreign Investment Risk—investments in foreign issuers involve additional risks (such as risks arising from less frequent trading, changes in political or social conditions, and less publicly available information about non-U.S. issuers) that differ from those associated with investments in U.S. issuers and may result in greater price volatility.

High Portfolio Turnover Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

High Portfolio Turnover Risk—higher portfolio turnover may adversely affect Fund performance by increasing Fund transaction costs and may increase a shareholder’s tax liability.

Master Limited Partnership Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Master Limited Partnership Risk—investments in master limited partnerships are subject to similar risks to those associated with the specific industry or industries in which the partnership invests, such as the risk of investing in the real estate or oil and gas industries. In addition, investments in master limited partnerships are subject to the risks of investing in a partnership, including limited control and voting rights on matters affecting the partnership and fewer investor protections compared to corporations.

PTP Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

PTP Risk— investing in PTPs (including master limited partnerships) involves special risks in addition to those typically associated with publicly traded companies. PTPs are exposed to the risks of their underlying assets, which in many cases includes the same types of risks as energy and natural resources companies, such as commodity pricing risk, supply and demand risk and depletion and exploration risk. PTPs are also subject to capital markets risk, which is the risk that they may be unable to raise capital to execute their growth strategies. PTPs are also subject to tax risk, which is the risk that PTPs may lose their

partnership status for tax purposes. The Fund’s ability to make investments in certain PTPs, including master limited partnerships, can be limited by the Fund’s intention to qualify as a regulated investment company accorded favorable tax treatment under the Internal Revenue Code, and if the Fund does not appropriately limit such investments or if such investments are recharacterized for U.S. federal income tax purposes, the Fund’s status as a regulated investment company may be jeopardized.

Real Estate Industry Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Real Estate Industry Risk—investments in the Fund may be subject to many of the same risks as a direct investment in real estate. The stock prices of companies in the real estate industry, including REITs, are typically sensitive to changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use, and rents, as well as the management skill and creditworthiness of the issuer. Investments in the real estate sector also may be adversely impacted by natural or environmental disasters. REITs also depend generally on their ability to generate cash flow to make distributions to shareholders or unitholders and are subject to the risk of failing to qualify for favorable tax treatment under the Internal Revenue Code.

Sector Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Sector Risk—issuers and companies that are in similar industry sectors may be similarly affected by particular economic or market events; to the extent the Fund has substantial holdings within a particular sector, the risks associated with that sector increase. Stocks in the financials sector may comprise a significant portion of the Fund's portfolio. Unique risks of the financials sector include, but are not limited to, government regulation uncertainty, yield curve fluctuation, asset flow fluctuation, and capital market fluctuations.

Value Stock Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

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.

Market Risks [Member]

Prospectus [Line Items]

Risk [Text Block]

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.

Risk Lose Money [Member]

Prospectus [Line Items]

Risk [Text Block]

There is the risk that you may lose money on your investment.

Risk Not Insured Depository Institution [Member]

Prospectus [Line Items]

Risk [Text Block]

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.

Risk Nondiversified Status [Member]

Prospectus [Line Items]

Risk [Text Block]

Non-Diversified Fund Risk—the Fund is non-diversified and therefore a greater percentage of holdings may be focused in a small number of issuers or a single issuer, which can place the Fund at greater risk. Notwithstanding the Fund’s status as a “non-diversified” investment company under the Investment Company Act of 1940 (the “1940 Act”), the Fund intends to qualify each year as a regulated investment company accorded favorable tax treatment under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”), which imposes its own diversification requirements that are less restrictive than the requirements applicable to “diversified” investment companies under the 1940 Act. The Fund’s intention to qualify as a regulated investment company may limit its pursuit of its investment strategy and its investment strategy could limit its ability to so qualify.