Income Taxes - Components of Income (Loss) Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax [Line Items]
Total	$ (1,006)	$ (852)	$ (7,992)
United States
Income Tax [Line Items]
Domestic	(928)	(1,249)	(8,099)
Foreign
Income Tax [Line Items]
Foreign	$ (78)	$ 397	$ 107