Income Taxes - Reconciliation of the Provision for Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense at the federal statutory rate of 35%	$ 113	$ 100	$ 99
Foreign rate differential	(49)	(41)	(25)
State income taxes, net of effect of federal tax benefit	13	8	5
Unrecognized tax benefits and related interest	14	9	5
Non-deductible transaction costs	1
Change in valuation allowance	5	2	2
Other, net	(1)	1	1
Provision for income taxes	$ 96	$ 79	$ 87