Deferred Revenue - Schedule of Deferred Revenue Estimate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Revenue Arrangement [Line Items]
2018	$ 121
2019	45
2020	34
2021	25
2022	19
Thereafter	20
Total	264	$ 237	$ 190
Original Listing fee
Deferred Revenue Arrangement [Line Items]
2018	14
2019	12
2020	12
2021	11
2022	10
Thereafter	18
Total	77	66	50
Other Listing Fee
Deferred Revenue Arrangement [Line Items]
2018	24
2019	28
2020	21
2021	14
2022	9
Thereafter	2
Total	98	83	59
Data Services and Other Revenues
Deferred Revenue Arrangement [Line Items]
2018	83
2019	5
2020	1
2021	0
2022	0
Thereafter	0
Total	$ 89	$ 88	$ 81