REGULATORY CAPITAL (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Cboe Trading
Regulatory Requirement
Minimum net capital required to be maintained, option 1 - percentage of aggregate indebtedness items	6.67%
Minimum net capital required to be maintained, option 2 - amount	$ 0.1
Net capital	8.2
Excess net capital	7.6
Required net capital	0.6
Cboe Europe Equities
Regulatory Requirement
Financial resources requirement	22.9
Capital in excess of financial resources requirement	30.8
Cboe Chi-X Europe
Regulatory Requirement
Capital resources requirement	0.1
Capital in excess of capital resources requirement	0.5
Cboe SEF
Regulatory Requirement
Annual operating expenses for swap execution facility capital adequacy tests	0.5
XX month operating expenses for swap execution facility capital adequacy tests	0.8
CFE
Regulatory Requirement
Annual operating expenses for registered futures exchange capital adequacy tests	59.2
XX month operating expenses for registered futures exchange capital adequacy tests	$ 29.6