S000023781 [Member] Investment Strategy - AMG GW&K Municipal Enhanced Yield Fund	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	In pursuing its investment objective, which is a fundamental policy that may not be changed without shareholder approval, the Fund, under normal circumstances, invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in U.S. dollar-denominated fixed income securities that are exempt from federal income tax. This policy is also fundamental and may not be changed without shareholder approval. In addition, up to 50% of the Fund’s net assets, plus the amount of any borrowings for investment purposes, may be invested in securities that are subject to the federal alternative minimum tax. The Fund may invest up to 35% of its total assets in unrated securities, and may invest up to 50% of its total assets in unrated securities and below investment grade securities (commonly known as “junk bonds” or “high yield securities”). Below investment grade securities are rated below Baa3 by Moody’s Investors Service, Inc. (“Moody’s”) or below BBB- by S&P Global Ratings (“S&P”) or similarly rated by another nationally recognized statistical rating organization (“NRSRO”), or unrated but determined by GW&K Investment Management, LLC, the subadviser to the Fund (“GW&K” or the “Subadviser”), to be of comparable credit quality. In cases where the credit ratings agencies have assigned different credit ratings to the same security, the Fund will use the median rating when three NRSROs provide ratings (split-to-middle). When ratings are available from only two NRSROs, the Fund will assign the lower of the two ratings (split-to-low). The Fund may continue to hold securities that are downgraded in credit rating subsequent to their purchase if GW&K believes it would be advantageous to do so. The Fund may invest in bonds of any maturity or duration and does not expect to target any specific range of maturity or duration. The Fund’s average weighted portfolio maturity and average effective duration will vary from time to time depending on the Subadviser’s views on the direction of interest rates. Although the Fund seeks to be diversified by geography and across sectors of the municipal bond market, the Fund may at times invest a significant portion of its assets in a particular state or region or in a particular sector due to market conditions. GW&K may also allocate a significant portion of the Fund to a specific segment of the municipal bond yield. In particular, the Fund often favors bonds with more than 10 years to maturity that offer higher yields.

In pursuing its investment objective, which is a fundamental policy that may not be changed without shareholder approval, the Fund, under normal circumstances, invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in U.S. dollar-denominated fixed income securities that are exempt from federal income tax. This policy is also fundamental and may not be changed without shareholder approval. In addition, up to 50% of the Fund’s net assets, plus the amount of any borrowings for investment purposes, may be invested in securities that are subject to the federal alternative minimum tax.

The Fund may invest up to 35% of its total assets in unrated securities, and may invest up to 50% of its total assets in unrated securities and below investment grade securities (commonly known as “junk bonds” or “high yield securities”). Below investment grade securities are rated below Baa3 by Moody’s Investors Service, Inc. (“Moody’s”) or below BBB- by S&P Global Ratings (“S&P”) or similarly rated by another nationally recognized statistical rating organization (“NRSRO”), or unrated but determined by GW&K Investment Management, LLC, the subadviser to the Fund (“GW&K” or the “Subadviser”), to be of comparable credit quality. In cases where the credit ratings

agencies have assigned different credit ratings to the same security, the Fund will use the median rating when three NRSROs provide ratings (split-to-middle). When ratings are available from only two NRSROs, the Fund will assign the lower of the two ratings (split-to-low). The Fund may continue to hold securities that are downgraded in credit rating subsequent to their purchase if GW&K believes it would be advantageous to do so. The Fund may invest in bonds of any maturity or duration and does not expect to target any specific range of maturity or duration. The Fund’s average weighted portfolio maturity and average effective duration will vary from time to time depending on the Subadviser’s views on the direction of interest rates.

Although the Fund seeks to be diversified by geography and across sectors of the municipal bond market, the Fund may at times invest a significant portion of its assets in a particular state or region or in a particular sector due to market conditions. GW&K may also allocate a significant portion of the Fund to a specific segment of the municipal bond yield. In particular, the Fund often favors bonds with more than 10 years to maturity that offer higher yields.