Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective income tax rate	33.10%	35.00%	33.50%	34.50%
Unrecognized tax benefits	$ 86		$ 86		$ 82
Accrued interest and penalties associated with uncertain tax positions	$ 16		$ 16		$ 19