Health Care Costs Payable - Liability for Unpaid Claims and Claims Adjustment Expense (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Reinsurance recoverables	$ 5
Other non-insurance health care costs payable	1,292
Total health care costs payable	12,049
Health Insurance Product Line
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total outstanding liabilities for health care costs payable, net of reinsurance	10,535
Reinsurance recoverables	5	$ 5	$ 8	$ 10
Insurance lines other than short duration	$ 217
Total health care costs payable		$ 10,142