Supplementary Information - Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Allowance for doubtful accounts
Balance at beginning of year	$ 373	$ 323
Provision	72	66
Write-offs & other	(45)	(16)
Balance at end of year	$ 400	$ 373