0001004434 2024-03-14 2024-03-14 0001004434 us-gaap:CommonStockMember 2024-03-14 2024-03-14 0001004434 amg:FivePointEightSeventyFiveJuniorSubordinatedNotesDue2059Member 2024-03-14 2024-03-14 0001004434 amg:FourPointSevenFivePercentJuniorSubordinatedNotesDue2060Member 2024-03-14 2024-03-14 0001004434 amg:FourPointTwoPercentJuniorSubordinatedNotesDue2061Member 2024-03-14 2024-03-14 false 0001004434 8-K 2024-03-14 AFFILIATED MANAGERS GROUP, INC. DE 001-13459 04-3218510 777 South Flagler Drive West Palm Beach FL 33401 (800) 345-1100 false false false false Common Stock ($0.01 par value) AMG NYSE 5.875% Junior Subordinated Notes due 2059 MGR NYSE 4.750% Junior Subordinated Notes due 2060 MGRB NYSE 4.200% Junior Subordinated Notes due 2061 MGRD NYSE false