Income Taxes - Components of Income/(Loss) Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of Income/(Loss) Before Income Taxes [Line Items]
Income/(loss) from continuing operations before income taxes	$ 183	$ (2,370)	$ (6,131)
United States [Member]
Components of Income/(Loss) Before Income Taxes [Line Items]
Income/(loss) from continuing operations before income taxes	205	(2,374)	(6,129)
Outside of the U.S. [Member]
Components of Income/(Loss) Before Income Taxes [Line Items]
Income/(loss) from continuing operations before income taxes	$ (22)	$ 4	$ (2)