Deferred Revenue (Changes in Deferred Revenue) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	$ 274
Deferred revenue billed in the current period, net of recognition	279
Revenue recognized that was included in the beginning of the period	(78)
Translation adjustment	(3)
Ending balance	472
Initial Listing Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	69
Deferred revenue billed in the current period, net of recognition	7
Revenue recognized that was included in the beginning of the period	(10)
Translation adjustment	0
Ending balance	66
Annual Listings Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	2
Deferred revenue billed in the current period, net of recognition	181
Revenue recognized that was included in the beginning of the period	(1)
Translation adjustment	0
Ending balance	182
Corporate Solutions Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	41
Deferred revenue billed in the current period, net of recognition	21
Revenue recognized that was included in the beginning of the period	(18)
Translation adjustment	0
Ending balance	44
Information Services Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	82
Deferred revenue billed in the current period, net of recognition	48
Revenue recognized that was included in the beginning of the period	(26)
Translation adjustment	0
Ending balance	104
Market Technology Revenues
Change in Contract with Customer Liability [Roll Forward]
Beginning balance	66
Deferred revenue billed in the current period, net of recognition	16
Revenue recognized that was included in the beginning of the period	(18)
Translation adjustment	(4)
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	6
Revenue recognized that was included in the beginning of the period	(5)
Translation adjustment	1
Ending balance	$ 16