Accounts Receivable, Net (Allowance for Credit Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 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)	(20)	47
Write-offs charged against the allowance for expected credit losses	(5)	(2)
Other, net(2)	(1)	9
Balance as of March 31,	$ 520	308
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)		$ 38