Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ 28	$ 12	$ 46	$ (28)
Effective tax provision (benefit) rate (as a percent)	37.20%	31.80%	37.00%	(34.70%)
Unrecognized tax benefits, recognition period (in months)			12 months