EMPLOYEE BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
SMART Plan
Defined Contribution Plan
Company contribution amount	$ 3.6	$ 2.1	$ 5.2	$ 4.0
Balance amount in the plan			20.3
Cboe Europe Equities Employee Selected Stakeholder Contribution Plan
Defined Contribution Plan
Company contribution amount	$ 0.1	$ 0.1	$ 0.4	$ 0.3