Deferred Revenue - Schedule of Deferred Revenue Recognized (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Remainder of 2018	$ 453
2019	48
2020	27
2021	18
2022	12
Thereafter	2
Total	560	$ 216	$ 521	$ 194
Annual Listings Revenue
Deferred Revenue Arrangement [Line Items]
Remainder of 2018	285
2019	0
2020	0
2021	0
2022	0
Thereafter	0
Total	285	0	270	0
Original Listing Revenues
Deferred Revenue Arrangement [Line Items]
Remainder of 2018	18
2019	8
2020	0
2021	0
2022	0
Thereafter	0
Total	26	25	20	23
Other Listing Revenues
Deferred Revenue Arrangement [Line Items]
Remainder of 2018	18
2019	31
2020	25
2021	17
2022	12
Thereafter	2
Total	105	98	95	83
Data Services and Other Revenues
Deferred Revenue Arrangement [Line Items]
Remainder of 2018	132
2019	9
2020	2
2021	1
2022	0
Thereafter	0
Total	$ 144	$ 93	$ 136	$ 88