Credit Losses on Financial Instruments (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at January 1, 2020	$ 35
Provision for expected losses	45
Write-offs charged against the allowance	(38)
Recoveries collected	6
Ending balance at September 30, 2020	48
Business
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at January 1, 2020	17
Provision for expected losses	23
Write-offs charged against the allowance	(16)
Recoveries collected	3
Ending balance at September 30, 2020	27
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance at January 1, 2020	18
Provision for expected losses	22
Write-offs charged against the allowance	(22)
Recoveries collected	3
Ending balance at September 30, 2020	$ 21