FAIR VALUE MEASUREMENT - Fair value hierarchy for assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Assets:
Total assets	$ 115.5		$ 37.1
Digital assets - safeguarded assets	22.9	$ 22.4
Liabilities:
Contingent consideration liabilities	39.1		70.5
Digital assets - safeguarded liabilities	22.9	$ 22.4
Cboe Digital restricted common units liability	15.5
Cboe Digital warrant liability	5.9
Total liabilities	1,684.8		1,432.1
Level 1
Assets:
Total assets	115.5		37.1
Digital assets - safeguarded assets	22.9
Liabilities:
Digital assets - safeguarded liabilities	22.9
Total liabilities	50.4		28.0
Level 2
Liabilities:
Total liabilities	1,573.9		1,333.6
Level 3
Liabilities:
Contingent consideration liabilities	39.1		70.5
Cboe Digital restricted common units liability	15.5
Cboe Digital warrant liability	5.9
Total liabilities	60.5		70.5
Recurring
Assets:
Total assets	114.6
Digital assets - safeguarded assets	22.9
Liabilities:
Contingent consideration liabilities	39.1		70.5
Digital assets - safeguarded liabilities	22.9
Cboe Digital restricted common units liability	15.5
Cboe Digital warrant liability	5.9
Total liabilities	83.4		70.5
Recurring | U.S. Treasury securities
Assets:
Total assets	64.2		9.1
Recurring | Marketable securities
Assets:
Total assets			37.1
Recurring | Marketable securities | Mutual funds
Assets:
Total assets	15.3		18.4
Recurring | Marketable securities | Money market funds
Assets:
Total assets	12.2		9.6
Recurring | Level 1
Assets:
Total assets	114.6
Digital assets - safeguarded assets	22.9
Liabilities:
Digital assets - safeguarded liabilities	22.9
Total liabilities	22.9
Recurring | Level 1 | U.S. Treasury securities
Assets:
Total assets	64.2		9.1
Recurring | Level 1 | Marketable securities
Assets:
Total assets			37.1
Recurring | Level 1 | Marketable securities | Mutual funds
Assets:
Total assets	15.3		18.4
Recurring | Level 1 | Marketable securities | Money market funds
Assets:
Total assets	12.2		9.6
Recurring | Level 3
Liabilities:
Contingent consideration liabilities	39.1		70.5
Cboe Digital restricted common units liability	15.5
Cboe Digital warrant liability	5.9
Total liabilities	$ 60.5		$ 70.5