0001004434 2026-06-09 2026-06-09 0001004434 us-gaap:CommonStockMember 2026-06-09 2026-06-09 0001004434 amg:FivePointEightSeventyFiveJuniorSubordinatedNotesDue2059Member 2026-06-09 2026-06-09 0001004434 amg:FourPointSeventyFiveJuniorSubordinatedNotesDue2060Member 2026-06-09 2026-06-09 0001004434 amg:FourPointTwoJuniorSubordinatedNotesDue2061Member 2026-06-09 2026-06-09 0001004434 amg:SixPointSeventyFiveJuniorSubordinatedNotesDue2064Member 2026-06-09 2026-06-09 false 0001004434 8-K 2026-06-09 AFFILIATED MANAGERS GROUP, INC. DE 001-13459 04-3218510 1001 U.S. Highway One North Jupiter FL 33477 (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 6.750% Junior Subordinated Notes due 2064 MGRE NYSE false