Supplemental Information for the Consolidated Statements of Cash Flows - Cash Payments For Interest Costs And Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Interest costs (none capitalized)	$ 2,947	$ 3,475	$ 2,941
Income taxes	$ 97	$ 60	$ 68