Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective income tax rate	39.20%	32.40%	35.10%	33.60%
Unrecognized tax benefits	$ 93		$ 93		$ 82
Accrued interest and penalties associated with uncertain tax positions	$ 16		$ 16		$ 19