Revenues And Accounts Receivable - Allowance for Credit Loss (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($)
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 54
Provisions for credit losses	23
Write-offs	(15)
Ending balance	60
Distribution customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	19
Provisions for credit losses	3
Write-offs	(6)
Ending balance	17
Advertising and other customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	35
Provisions for credit losses	20
Write-offs	(9)
Ending balance	43
Cumulative Effect, Period Of Adoption, Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(2)
Cumulative Effect, Period Of Adoption, Adjustment | Distribution customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1
Cumulative Effect, Period Of Adoption, Adjustment | Advertising and other customers
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ (3)