Deferred Revenue - Schedule of Deferred Revenue Estimate (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
2019	$ 135
2020	38
2021	23
2022	15
2023	6
Thereafter	0
Total	217	$ 216	$ 198
Other Listing Revenues
Disaggregation of Revenue [Line Items]
2019	29
2020	29
2021	21
2022	15
2023	6
Thereafter	0
Total	100	98	83
Original Listing Revenues
Disaggregation of Revenue [Line Items]
2019	19
2020	6
2021	0
2022	0
2023	0
Thereafter	0
Total	25	25	23
Data Services and Other Revenues
Disaggregation of Revenue [Line Items]
2019	87
2020	3
2021	2
2022	0
2023	0
Thereafter	0
Total	$ 92	$ 93	$ 92