REVENUE RECOGNITION - Revenue by product line and Segment (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) item	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information
Number of types of regulatory fees the Company recognizes \| item	2
Revenues	$ 3,958.5	$ 3,494.8	$ 3,427.1
Services transferred at a point in time
Segment Reporting Information
Revenues	3,352.1	2,962.0	2,958.4
Services transferred over time
Segment Reporting Information
Revenues	606.4	532.8	468.7
Corporate Items and Eliminations
Segment Reporting Information
Revenues		0.3
Corporate Items and Eliminations \| Services transferred at a point in time
Segment Reporting Information
Revenues		0.3
Options \| Operating Segments
Segment Reporting Information
Revenues	1,823.2	1,505.0	1,330.1
Options \| Operating Segments \| Services transferred at a point in time
Segment Reporting Information
Revenues	1,562.8	1,296.7	1,148.9
Options \| Operating Segments \| Services transferred over time
Segment Reporting Information
Revenues	260.4	208.3	181.2
North American Equities \| Operating Segments
Segment Reporting Information
Revenues	1,681.7	1,570.5	1,789.5
North American Equities \| Operating Segments \| Services transferred at a point in time
Segment Reporting Information
Revenues	1,441.2	1,337.9	1,568.3
North American Equities \| Operating Segments \| Services transferred over time
Segment Reporting Information
Revenues	240.5	232.6	221.2
Futures \| Operating Segments
Segment Reporting Information
Revenues	119.8	120.6	109.2
Futures \| Operating Segments \| Services transferred at a point in time
Segment Reporting Information
Revenues	91.9	95.3	85.6
Futures \| Operating Segments \| Services transferred over time
Segment Reporting Information
Revenues	27.9	25.3	23.6
Europe and Asia Pacific \| Operating Segments
Segment Reporting Information
Revenues	264.6	240.3	140.5
Europe and Asia Pacific \| Operating Segments \| Services transferred at a point in time
Segment Reporting Information
Revenues	197.5	183.5	106.5
Europe and Asia Pacific \| Operating Segments \| Services transferred over time
Segment Reporting Information
Revenues	67.1	56.8	34.0
Global FX \| Operating Segments
Segment Reporting Information
Revenues	68.9	58.1	57.8
Global FX \| Operating Segments \| Services transferred at a point in time
Segment Reporting Information
Revenues	58.4	48.3	49.1
Global FX \| Operating Segments \| Services transferred over time
Segment Reporting Information
Revenues	10.5	9.8	8.7
Digital \| Operating Segments
Segment Reporting Information
Revenues	0.3
Digital \| Operating Segments \| Services transferred at a point in time
Segment Reporting Information
Revenues	0.3
Transaction and clearing fees
Segment Reporting Information
Revenues	2,938.8	2,693.1	2,418.0
Transaction and clearing fees \| Options \| Operating Segments
Segment Reporting Information
Revenues	1,471.7	1,231.2	1,046.3
Transaction and clearing fees \| North American Equities \| Operating Segments
Segment Reporting Information
Revenues	1,155.3	1,173.1	1,147.2
Transaction and clearing fees \| Futures \| Operating Segments
Segment Reporting Information
Revenues	91.6	95.2	84.5
Transaction and clearing fees \| Europe and Asia Pacific \| Operating Segments
Segment Reporting Information
Revenues	161.9	145.3	90.9
Transaction and clearing fees \| Global FX \| Operating Segments
Segment Reporting Information
Revenues	58.0	48.3	49.1
Transaction and clearing fees \| Digital \| Operating Segments
Segment Reporting Information
Revenues	0.3
Access and capacity fees
Segment Reporting Information
Revenues	324.2	280.7	236.7
Access and capacity fees \| Options \| Operating Segments
Segment Reporting Information
Revenues	151.7	124.0	107.0
Access and capacity fees \| North American Equities \| Operating Segments
Segment Reporting Information
Revenues	109.3	98.0	84.2
Access and capacity fees \| Futures \| Operating Segments
Segment Reporting Information
Revenues	19.9	18.7	17.0
Access and capacity fees \| Europe and Asia Pacific \| Operating Segments
Segment Reporting Information
Revenues	34.0	31.2	20.6
Access and capacity fees \| Global FX \| Operating Segments
Segment Reporting Information
Revenues	9.3	8.8	7.9
Market data fees
Segment Reporting Information
Revenues	282.2	252.1	232.0
Market data fees \| Options \| Operating Segments
Segment Reporting Information
Revenues	108.7	84.3	74.2
Market data fees \| North American Equities \| Operating Segments
Segment Reporting Information
Revenues	131.2	134.6	137.0
Market data fees \| Futures \| Operating Segments
Segment Reporting Information
Revenues	8.0	6.6	6.6
Market data fees \| Europe and Asia Pacific \| Operating Segments
Segment Reporting Information
Revenues	33.1	25.6	13.4
Market data fees \| Global FX \| Operating Segments
Segment Reporting Information
Revenues	1.2	1.0	0.8
Regulatory fees
Segment Reporting Information
Revenues	364.7	208.3	500.2
Regulatory fees \| Options \| Operating Segments
Segment Reporting Information
Revenues	84.2	46.6	83.4
Regulatory fees \| North American Equities \| Operating Segments
Segment Reporting Information
Revenues	280.2	161.6	416.8
Regulatory fees \| Futures \| Operating Segments
Segment Reporting Information
Revenues	0.3	0.1
Other revenue
Segment Reporting Information
Revenues	48.6	60.6	40.2
Other revenue \| Corporate Items and Eliminations
Segment Reporting Information
Revenues		0.3
Other revenue \| Options \| Operating Segments
Segment Reporting Information
Revenues	6.9	18.9	19.2
Other revenue \| North American Equities \| Operating Segments
Segment Reporting Information
Revenues	5.7	3.2	4.3
Other revenue \| Futures \| Operating Segments
Segment Reporting Information
Revenues			1.1
Other revenue \| Europe and Asia Pacific \| Operating Segments
Segment Reporting Information
Revenues	35.6	38.2	15.6
Other revenue \| Global FX \| Operating Segments
Segment Reporting Information
Revenues	0.4
Licensing revenue
Segment Reporting Information
Revenues		12.4	13.1
Cash and spot markets
Segment Reporting Information
Revenues	1,777.6	1,660.5	1,820.1
Cash and spot markets \| Transaction and clearing fees
Segment Reporting Information
Revenues	1,375.5	1,366.5	1,287.2
Cash and spot markets \| Market data fees
Segment Reporting Information
Revenues	80.3	91.6	98.6
Cash and spot markets \| Regulatory fees
Segment Reporting Information
Revenues	280.2	161.6	416.9
Cash and spot markets \| Other revenue
Segment Reporting Information
Revenues	41.6	40.8	17.4
Data and access solutions
Segment Reporting Information
Revenues	497.0	427.7	360.5
Data and access solutions \| Access and capacity fees
Segment Reporting Information
Revenues	324.2	280.7	236.7
Data and access solutions \| Market data fees
Segment Reporting Information
Revenues	168.7	130.0	105.0
Data and access solutions \| Other revenue
Segment Reporting Information
Revenues	4.1	17.0	18.8
Derivatives markets
Segment Reporting Information
Revenues	1,683.9	1,406.6	1,246.5
Derivatives markets \| Transaction and clearing fees
Segment Reporting Information
Revenues	1,563.3	1,326.6	1,130.8
Derivatives markets \| Market data fees
Segment Reporting Information
Revenues	33.2	30.5	28.4
Derivatives markets \| Regulatory fees
Segment Reporting Information
Revenues	84.5	46.7	83.3
Derivatives markets \| Other revenue
Segment Reporting Information
Revenues	$ 2.9	$ 2.8	$ 4.0