Revenue Recognition - Schedule of Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	$ 1,580.0
Revenues, less transaction-based expenses	1,225.0	$ 1,166.0
Services transferred over time	63.0	57.0
Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	951.0
Revenues, less transaction-based expenses	596.0	538.0
Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	629.0
Revenues, less transaction-based expenses	629.0	628.0
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	509.0	458.0
Services transferred at a point in time | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	509.0	458.0
Services transferred at a point in time | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	0.0	0.0
Services transferred over time
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	716.0	708.0
Services transferred over time | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	87.0	80.0
Services transferred over time | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	629.0	628.0
Transaction and clearing, net
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	898.0	798.0
Transaction and clearing, net | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	898.0	798.0
Transaction and clearing, net | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	0.0	0.0
Data services
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	520.0	520.0
Data services | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	0.0	0.0
Data services | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	520.0	520.0
Listings
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	109.0	108.0
Listings | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	0.0	0.0
Listings | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	109.0	108.0
Other revenues
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	53.0	45.0
Other revenues | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	53.0	45.0
Other revenues | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	0.0	0.0
Total revenues
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax		1,471.0
Total revenues | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax		843.0
Total revenues | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax		628.0
Transaction-based expenses
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	355.0	305.0
Transaction-based expenses | Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	355.0	305.0
Transaction-based expenses | Data and Listings Segment
Disaggregation of Revenue [Line Items]
Revenues from contract with customer, excluding assessed tax	$ 0.0	$ 0.0