Class I [Member] Investment Strategy - Class I - AMG Yacktman Fund	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	The Fund invests primarily in domestic equity securities. The Fund, however, also may invest in foreign equity securities, including emerging market securities, and debt securities. The Fund may invest up to 30% of its assets in foreign equity securities. This 30% limit does not apply to investments in the form of American Depositary Receipts (“ADRs”). The Fund's investments in equity securities may include common stocks, preferred stocks, convertible preferred stocks and ADRs. Some, but not all, of the equity securities will pay a dividend. The Fund's investments in debt securities may include U.S. Treasury notes and bonds, investment grade corporate debt securities, convertible debt securities and debt securities below investment grade (high yield or junk bonds). The Fund may invest up to 20% of its assets in such debt securities, including junk bonds, in any proportion provided that the total invested does not exceed the 20% threshold at the time of investment. The Fund's subadviser, Yacktman Asset Management LP (“Yacktman” or the “Subadviser”), employs a disciplined investment strategy. The Fund invests in securities of any size company at levels the Subadviser believes offer an attractive forward rate of return. When the Subadviser purchases stocks, it generally searches for companies that it believes possess one or more of the following three attributes: (1) good business; (2) shareholder-oriented management; or (3) low purchase price. The Fund generally sells companies that no longer meet its investment criteria, or if better investment opportunities are available. Under normal market conditions, the majority of the Fund’s assets will be allocated to equity securities. The Fund may hold assets in cash and cash equivalents, and at times these holdings may be significant. The Fund’s cash level at any point typically relates to the Subadviser’s individual security selection process, and therefore may vary, depending on the Subadviser’s desired security weightings.

The Fund invests primarily in domestic equity securities. The Fund, however, also may invest in foreign equity securities, including emerging market securities, and debt securities.

The Fund may invest up to 30% of its assets in foreign equity securities. This 30% limit does not apply to investments in the form of American Depositary Receipts (“ADRs”). The Fund's investments in equity securities may include common stocks, preferred stocks, convertible preferred stocks and ADRs. Some, but not all, of the equity securities will pay a dividend.

The Fund's investments in debt securities may include U.S. Treasury notes and bonds, investment grade corporate debt securities, convertible debt securities and debt securities below investment grade (high yield or junk bonds). The Fund may invest up to 20% of its assets in such debt securities, including junk bonds, in any proportion provided that the total invested does not exceed the 20% threshold at the time of investment.

The Fund's subadviser, Yacktman Asset Management LP (“Yacktman” or the “Subadviser”), employs a disciplined investment strategy. The Fund invests in securities of any size company at levels the Subadviser believes offer an attractive forward rate of return. When the Subadviser purchases stocks, it generally searches for companies that it believes possess one or more of the following three attributes: (1) good business; (2) shareholder-oriented management; or (3) low purchase price. The Fund generally sells companies that no longer meet its investment criteria, or if better investment opportunities are available.

Under normal market conditions, the majority of the Fund’s assets will be allocated to equity securities. The Fund may hold assets in cash and cash equivalents, and at times these holdings may be significant. The Fund’s cash level at any point typically relates to the Subadviser’s individual security selection process, and therefore may vary, depending on the Subadviser’s desired security weightings.