(Accounts And Notes Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts and notes receivable	$ 3,064	$ 3,280
Trade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts and notes receivable	2,776	3,020
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts and notes receivable	$ 288	$ 260