Income Taxes - Summary of the Components of Our Provision for Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current income tax expense:
Federal	$ 93	$ 48	$ 56
State	14	9	6
Foreign	6	17	30
Current income tax expense	113	74	92
Deferred income tax (benefit) expense:
Federal	(12)	6	(3)
State	(1)	1
Foreign	(4)	(2)	(2)
Deferred income tax (benefit) expense:	(17)	5	(5)
Provision for income taxes	$ 96	$ 79	$ 87