Credit Losses on Financial Instruments (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 61
Provision for expected losses	18
Write-offs charged against the allowance	(50)
Recoveries collected	10
Ending balance	39
Consumer Reclassed to Mass Market
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	32
Business Reclassed to Mass Markets
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4
Mass Market Portfolio
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	36
Provision for expected losses	12
Write-offs charged against the allowance	(35)
Recoveries collected	8
Ending balance	21
Business Portfolio
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	25
Provision for expected losses	6
Write-offs charged against the allowance	(15)
Recoveries collected	2
Ending balance	$ 18