Receivables, Loans, Notes Receivable, and Others (Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Allowance for expected credit losses	$ 546	$ 254
Current period provision for expected credit losses(1)	277
Write-offs charged against the allowance for expected credit losses	(5)
Other, net(2)	20
Cumulative Effect, Period of Adoption, Adjustment [Member]
Accounts Notes And Loans Receivable [Line Items]
Other, net(2)	34
COVID 19 [Member]
Accounts Notes And Loans Receivable [Line Items]
Current period provision for expected credit losses(1)	$ 248