FAIR VALUE MEASUREMENT - Changes in fair value of Level 3 financial assets (Details) - Level 3 - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
Assets:
Balance at Beginning of Period	$ 6.4	$ 0.0
Realized (Losses) Gains during Period	0.0	(0.6)
Adjustments	0.0	0.0
Additions	0.0	7.0
Settlements	0.0	0.0
Foreign Currency Translation	0.0	0.0
Balance at End of Period	6.4	6.4
Liabilities:
Balance at Beginning of Period	1.8	36.4
Realized Losses (Gains) during Period	(1.0)	(0.4)
Adjustments	0.0	(16.2)
Additions	0.0	0.0
Settlements	(0.9)	(19.9)
Foreign Currency Translation	0.1	0.1
Balance at End of Period	0.0	0.0
Contingent consideration liabilities
Liabilities:
Balance at Beginning of Period	1.8	11.8
Realized Losses (Gains) during Period	(1.0)	2.0
Adjustments	0.0	0.0
Additions	0.0	0.0
Settlements	(0.9)	(13.9)
Foreign Currency Translation	0.1	0.1
Balance at End of Period	0.0	0.0
Cboe Digital restricted common units liability
Liabilities:
Balance at Beginning of Period		18.7
Realized Losses (Gains) during Period		(1.0)
Adjustments		(12.1)
Additions		0.0
Settlements		(5.6)
Foreign Currency Translation		0.0
Balance at End of Period	0.0	0.0
Cboe Digital warrant liability
Liabilities:
Balance at Beginning of Period		5.9
Realized Losses (Gains) during Period		(1.4)
Adjustments		(4.1)
Additions		0.0
Settlements		(0.4)
Foreign Currency Translation		0.0
Balance at End of Period	0.0	0.0
Allowance for notes receivable credit losses
Assets:
Balance at Beginning of Period	6.4	0.0
Realized (Losses) Gains during Period	0.0	(0.6)
Adjustments	0.0	0.0
Additions	0.0	7.0
Settlements	0.0	0.0
Foreign Currency Translation	0.0	0.0
Balance at End of Period	$ 6.4	$ 6.4