Debt - Summary of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014	Sep. 19, 2013
Debt Instrument [Line Items]
Gross Carrying Amount	$ 4,119	$ 4,369
Unamortized Discount	(42)	(45)
Net Carrying Amount	4,077	4,324
Term Loan
Debt Instrument [Line Items]
Gross Carrying Amount	1,869	2,119
Unamortized Discount	(9)	(10)
Net Carrying Amount	1,860	2,109
2021 Notes
Debt Instrument [Line Items]
Gross Carrying Amount	1,500	1,500	$ 1,500
Unamortized Discount	(22)	(23)
Net Carrying Amount	1,478	1,477
2023 Notes
Debt Instrument [Line Items]
Gross Carrying Amount	750	750	$ 750
Unamortized Discount	(11)	(12)
Net Carrying Amount	$ 739	$ 738