Credit Losses on Financial Instruments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 61
Provision for expected losses	7
Write-offs charged against the allowance	(17)
Recoveries collected	2
Ending balance	53
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	3
Write-offs charged against the allowance	(10)
Recoveries collected	1
Ending balance	30
Business Portfolio
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	25
Provision for expected losses	4
Write-offs charged against the allowance	(7)
Recoveries collected	1
Ending balance	$ 23