Deferred Revenue Deferred Revenue (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	$ 136
Additions	497
Amortization	(260)
Deferred revenue balance at June 30, 2015	373
Deferred revenue	294	$ 69
Deferred Revenue, Noncurrent	79
Annual Listing Fee Revenue
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	0
Additions	356
Amortization	(178)
Deferred revenue balance at June 30, 2015	178
Original Listing Fee Revenues
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	35
Additions	9
Amortization	(2)
Deferred revenue balance at June 30, 2015	42
Other Listing Fee Revenues
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	46
Additions	18
Amortization	(8)
Deferred revenue balance at June 30, 2015	56
Data Services Fees and Other Revenues
Movement in Deferred Revenue [Roll Forward]
Deferred revenue balance at December 31, 2014	55
Additions	114
Amortization	(72)
Deferred revenue balance at June 30, 2015	$ 97