GOODWILL AND INTANGIBLE ASSETS - Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Schedule of Intangible Assets and Goodwill [Line Items]
Goodwill	$ 2,642.8	$ 2,642.8
Total	2,917.0	3,010.9
Investment advisory agreements
Schedule of Intangible Assets and Goodwill [Line Items]
Definite-lived intangible assets - investment advisory agreements	125.9	216.5
Trade Names
Schedule of Intangible Assets and Goodwill [Line Items]
Indefinite-lived intangible assets - trade name	86.0	86.0
Investment advisory agreements
Schedule of Intangible Assets and Goodwill [Line Items]
Indefinite-lived intangible assets - trade name	$ 62.3	$ 65.6