Income Taxes (Schedule of Income Tax Provision and Effective Tax Rate) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Provision for income taxes	$ (20)	$ 65	$ 45	$ 166
Effective tax rate	(34.50%)	40.90%	9.80%	35.20%