Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 19	$ 22	$ 32	$ 43
Effective tax provision rate (as a percent)	31.80%	32.70%	32.30%	33.40%
Unrecognized tax benefits, recognition period (in months)			12 months