Accounts Receivable, Net (Allowance for Credit Loss) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance as of January 1	$ 546	$ 254
Current period provision for expected credit losses, net of recoveries (1)	(32)	263
Write-offs charged against the allowance for expected credit losses	(15)	(5)
Other, net(2)	(4)	18
Balance as of September 30	$ 495	530
ASU 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other, net(2)		34
COVID-19 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses, net of recoveries (1)		$ 223