Deferred Revenue (Changes in Deferred Revenue) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($)
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	$ 274
Deferred revenue billed in the current period, net of recognition	250
Revenue recognized that was included in the beginning of the period	(176)
Foreign currency translation adjustment	4
Ending balance	352
Initial Listing Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	69
Deferred revenue billed in the current period, net of recognition	29
Revenue recognized that was included in the beginning of the period	(24)
Foreign currency translation adjustment	1
Ending balance	75
Annual Listings Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	2
Deferred revenue billed in the current period, net of recognition	66
Revenue recognized that was included in the beginning of the period	(2)
Foreign currency translation adjustment	(1)
Ending balance	65
Corporate Solutions Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	41
Deferred revenue billed in the current period, net of recognition	44
Revenue recognized that was included in the beginning of the period	(39)
Foreign currency translation adjustment	0
Ending balance	46
Information Services Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	82
Deferred revenue billed in the current period, net of recognition	67
Revenue recognized that was included in the beginning of the period	(58)
Foreign currency translation adjustment	0
Ending balance	91
Market Technology Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	66
Deferred revenue billed in the current period, net of recognition	36
Revenue recognized that was included in the beginning of the period	(45)
Foreign currency translation adjustment	3
Ending balance	60
Other
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	14
Deferred revenue billed in the current period, net of recognition	8
Revenue recognized that was included in the beginning of the period	(8)
Foreign currency translation adjustment	1
Ending balance	$ 15