EMPLOYEE BENEFIT PLAN (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
SMART Plan
Defined Contribution Plan
Total assets in the trust			$ 20.9		$ 23.4
Company contribution amount	$ 2.6	$ 3.6	4.1	$ 5.2
Cboe Europe Equities Employee Selected Stakeholder Contribution Plan
Defined Contribution Plan
Company contribution amount	$ 0.2	$ 0.1	$ 0.4	$ 0.4