Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	32.60%	32.90%	32.40%	33.40%
Unrecognized tax benefits	$ 138		$ 138		$ 118
Accrued interest and penalties associated with uncertain tax positions	$ 27		$ 27		$ 23