FAIR VALUE MEASUREMENT - Changes in fair value of Level 3 financial liabilities (Details) - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Assets:
Balance at Beginning of Period	$ 6.2	$ 0.0
(Losses) Gains during Period	(0.8)
Adjustments	0.0
Additions	7.0
Settlements	0.0
Foreign Currency Translation	0.0
Liabilities:
Balance at Beginning of Period	36.4	60.5
Losses (Gains) during Period	(0.4)	(14.4)
Adjustments	(16.2)	0.1
Additions	0.0	3.1
Settlements	(19.9)	(13.1)
Foreign Currency Translation	0.1	0.2
Balance at End of Period	0.0	36.4
Contingent consideration liabilities
Liabilities:
Balance at Beginning of Period	11.8	39.1
Losses (Gains) during Period	2.0	(14.4)
Adjustments	0.0	0.0
Additions	0.0	0.0
Settlements	(13.9)	(13.1)
Foreign Currency Translation	0.1	0.2
Balance at End of Period	0.0	11.8
Cboe Digital restricted common units liability
Liabilities:
Balance at Beginning of Period	18.7	15.5
Losses (Gains) during Period	(1.0)	0.0
Adjustments	(12.1)	0.1
Additions	0.0	3.1
Settlements	(5.6)	0.0
Foreign Currency Translation	0.0	0.0
Balance at End of Period	0.0	18.7
Cboe Digital warrant liability
Liabilities:
Balance at Beginning of Period	5.9	5.9
Losses (Gains) during Period	(1.4)	0.0
Adjustments	(4.1)	0.0
Additions	0.0	0.0
Settlements	(0.4)	0.0
Foreign Currency Translation	0.0	0.0
Balance at End of Period	0.0	5.9
Allowance for notes receivable credit losses | Fair Value Option, Note Receivable
Assets:
Balance at Beginning of Period	6.2	$ 0.0
(Losses) Gains during Period	(0.8)
Adjustments	0.0
Additions	7.0
Settlements	0.0
Foreign Currency Translation	$ 0.0