Income Taxes (Schedule of Income (Loss) Before Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
United States	$ 642	$ (783)	$ (1,449)
Foreign	785	329	285
Income (loss) from continuing operations before income taxes	$ 1,427	$ (454)	$ (1,164)