Other Financial Statements Items - Schedule of Change in Allowance For Bad Debts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 69	$ 62	$ 64
Current period provision	83	92	74
Write-off as uncollectible	(44)	(85)	(76)
Ending balance	$ 108	$ 69	$ 62