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 at December 31, 2020	$ 45
Provision for expected losses	14
Write-offs charged against the allowance	(21)
Recoveries collected	4
Reclassified as held for sale	(3)
Ending balance at September 30, 2021	$ 39