S000001129 [Member] Investment Risks - AMG River Road Dividend All Cap Value Fund	Oct. 31, 2025
Small and Mid Capitalization Stock Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Small- and Mid-Capitalization Stock Risk—the stocks of small- and mid-capitalization companies often have greater price volatility, lower trading volume, and less liquidity than the stocks of larger, more established 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.
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.
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.
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.
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.
Liquidity Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	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.
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 of 1986, as amended (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.
Royalty Income Trust Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Royalty Income Trust Risk— investing in royalty income trusts, which typically passively manage royalties and net working interests in oil-, gas- or mineral-producing properties and rely on outside drilling or mining companies to extract the resources, involves certain risks not typically associated with investing in publicly traded companies. Royalty income trusts generally do not guarantee minimum distributions or return of capital. Royalty income trusts are also exposed to many of the same risks as energy and natural resources companies, such as commodity pricing risk, supply and demand risk and depletion and exploration risk.
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.

S000001129 [Member] Investment Risks - AMG River Road Dividend All Cap Value Fund

Oct. 31, 2025

Small- and Mid-Capitalization Stock Risk—the stocks of small- and mid-capitalization companies often have greater price volatility, lower trading volume, and less liquidity than the stocks of larger, more established companies.

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.

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.

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.

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.

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.

Liquidity Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

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.

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 of 1986, as amended (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.

Royalty Income Trust Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Royalty Income Trust Risk— investing in royalty income trusts, which typically passively manage royalties and net working interests in oil-, gas- or mineral-producing properties and rely on outside drilling or mining companies to extract the resources, involves certain risks not typically associated with investing in publicly traded companies. Royalty income trusts generally do not guarantee minimum distributions or return of capital. Royalty income trusts are also exposed to many of the same risks as energy and natural resources companies, such as commodity pricing risk, supply and demand risk and depletion and exploration risk.

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.