Accounts Receivable - Changes in Allowance for Fee-for-Service Commissions (Details) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($)
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance as of December 31, 2021	$ 39
Balance at March 31, 2022	48
Fee-for-service commission
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance as of December 31, 2021	18
Current period provision for expected credit losses	5
Write-offs charged against the allowance	(9)
Balance at March 31, 2022	$ 14