SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended		174 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025
Subsequent Events
Revenues less cost of revenues:		$ 587.3	$ 513.8	$ 1,152.5	$ 1,015.9
Number of shares of common stock repurchased (in shares)		160,564	514,239			21,063,700
Average price paid per share (in dollars per share)		$ 219.77	$ 175.76			$ 80.02
Total purchase price		$ 35.3	$ 90.4			$ 1,700.0
Availability remaining under existing share repurchase authorizations		614.5	$ 204.4	614.5	$ 204.4	$ 614.5
Cboe Japan | Europe and Asia Pacific
Subsequent Events
Revenues less cost of revenues:		$ 3.3		$ 7.6
Cboe Japan | Europe and Asia Pacific | Gross Profit Benchmark | Geographic Concentration Risk
Subsequent Events
Concentration risk, percentage of total revenue		5.00%		6.00%
Subsequent Event | Europe and Asia Pacific
Subsequent Events
Impairment of intangible assets	$ 4.6