Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	32.10%	33.90%
Unrecognized tax benefits	$ 137		$ 118
Accrued interest and penalties associated with uncertain tax positions	$ 25		$ 23