Deferred Revenue - Schedule of Changes in Deferred Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Roll Forward]
Deferred revenue, beginning balance	$ 217	$ 216
Additions	831	812
Amortization	(847)	(811)
Deferred revenue, ending balance	201	217
Annual Listing Revenue
Disaggregation Of Revenue [Roll Forward]
Deferred revenue, beginning balance	0	0
Additions	384	384
Amortization	(384)	(384)
Deferred revenue, ending balance	0	0
Original Listing Revenues
Disaggregation Of Revenue [Roll Forward]
Deferred revenue, beginning balance	25	25
Additions	17	24
Amortization	(23)	(24)
Deferred revenue, ending balance	19	25
Other Listing Revenues
Disaggregation Of Revenue [Roll Forward]
Deferred revenue, beginning balance	100	98
Additions	36	38
Amortization	(42)	(36)
Deferred revenue, ending balance	94	100
Data Services and Other Revenues
Disaggregation Of Revenue [Roll Forward]
Deferred revenue, beginning balance	92	93
Additions	394	366
Amortization	(398)	(367)
Deferred revenue, ending balance	$ 88	$ 92