Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective income tax rate	34.00%	33.70%
Unrecognized tax benefits	$ 88		$ 82
Accrued interest and penalties associated with uncertain tax positions	$ 19		$ 77