Health Care Costs Payable - Reconciliation of Health Care Net Incurred and Paid Claims Development to Health Care Costs Payable Liability (Details) - Health Insurance Product Line - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration health care costs payable, net of reinsurance	$ 8,574
Reinsurance recoverables	8	$ 10	$ 5	$ 4
Premium deficiency reserve	16	11	4
Insurance lines other than short duration	210
Total health care costs payable	$ 8,808	$ 7,936	$ 6,879	$ 6,147