ACQUISITIONS - Acquisition Summary (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023 USD ($) item	Sep. 30, 2024 USD ($) item	Sep. 30, 2023 USD ($)	Jun. 30, 2024 item	May 31, 2024 item	Dec. 31, 2023 USD ($)
Business Acquisition [Line Items]
Number of acquisitions | item	3
Number of other immaterial acquisitions | item		2		2	2
Goodwill		$ 7,898.7				$ 8,148.2
Prior year business combinations, goodwill adjustments		$ 0.6
Weighted average useful lives of definite-lived intangible assets acquired from other acquisitions		9 years	12 years
Global Institutional and Specialty
Business Acquisition [Line Items]
Goodwill		$ 611.6				$ 610.0
2023 and 2024 Acquisitions
Business Acquisition [Line Items]
Payments for merger related costs		3.3
Acquisition related liabilities and contingent consideration, purchase accounting adjustments		3.6
Net intangible assets purchase		2.1
Prior year business combinations, net intangible assets adjustments		1.0
Prior year business combinations, goodwill adjustments		0.8
Business Acquisitions and Investment
Business Acquisition [Line Items]
Net tangible assets (liabilities) acquired	$ 9.8	2.0	$ 9.8
Identifiable intangible assets	57.3	21.7	57.3
Goodwill	40.5	33.6	40.5
Total aggregate purchase price		57.3	107.6
Acquisition related liabilities and contingent consideration		(3.2)	(5.3)
Net cash paid for acquisitions, including acquisition-related liabilities and contingent consideration		54.1	102.3
Business Acquisitions and Investment | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	35.5	18.3	35.5
Business Acquisitions and Investment | Trademarks
Business Acquisition [Line Items]
Identifiable intangible assets		1.8
Business Acquisitions and Investment | Other technology
Business Acquisition [Line Items]
Identifiable intangible assets	$ 21.8	$ 1.6	$ 21.8