Deferred Revenue Deferred Revenue (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	$ 136
Additions	530
Amortization	(394)
Deferred revenue balance at September 30, 2015	272
Deferred revenue	186	$ 69
Deferred Revenue, Noncurrent	86
Annual Listing Fee Revenue
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	0
Additions	358
Amortization	(268)
Deferred revenue balance at September 30, 2015	90
Original Listing Fee Revenues
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	35
Additions	18
Amortization	(3)
Deferred revenue balance at September 30, 2015	50
Other Listing Fee Revenues
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	46
Additions	23
Amortization	(12)
Deferred revenue balance at September 30, 2015	57
Data Services Fees and Other Revenues
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	55
Additions	131
Amortization	(111)
Deferred revenue balance at September 30, 2015	$ 75