Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	25.90%	39.20%	30.70%	35.10%
Unrecognized tax benefits	$ 122		$ 122		$ 118
Accrued interest and penalties associated with uncertain tax positions	$ 30		$ 30		$ 23