INCOME TAXES - Net Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Deferred tax assets
Accrued, deferred, and long-term incentive compensation	$ 337.7	$ 317.7
Operating lease liability	81.5	39.8
Acquired investments	71.7	66.4
Net operating loss carry-forwards	64.8	53.7
Property, equipment and software	0.0	90.9
Other	27.0	12.9
Total deferred tax assets	582.7	581.4
Valuation allowances	(130.1)	(118.9)
Total deferred tax assets, net of valuation allowances	452.6	462.5
Deferred tax liabilities
Operating lease assets	(75.0)	(41.1)
Unrealized gains (losses) recognized in non-operating income	(66.6)	(50.0)
Acquisition-related liabilities	(64.0)	(77.5)
Property, equipment and software	(58.9)	0.0
Other	0.0	(15.9)
Total deferred tax liabilities	(264.5)	(184.5)
Net deferred tax assets	$ 188.1	$ 278.0