Health Care Costs Payable - Components of Change in Health Care Costs Payable (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Health care costs payable, beginning of the period	$ 10,142
Less: Claims paid
Health care costs payable, end of the period	12,550
Health Care Benefits
Less: Claims paid
Benefit costs recorded in other insurance liabilities	62	$ 59
Corporate / Other
Less: Claims paid
Benefit costs recorded in other insurance liabilities	163	204
Health Insurance Product Line
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Health care costs payable, beginning of the period	10,142	8,678
Less: Reinsurance recoverables	5	8
Less: Impact of discount rate on long-duration insurance reserves	8	0
Health care costs payable, beginning of the period, net	10,129	8,670
Acquisitions, net	1,098	0
Add: Components of incurred health care costs
Current year	64,183	53,216
Prior years	(679)	(670)
Total incurred health care costs	63,504	52,546
Less: Claims paid
Current year	52,952	43,632
Prior years	9,207	7,468
Total claims paid	62,159	51,100
Add: Premium deficiency reserve	0	5
Health care costs payable, end of the period, net	12,572	10,121
Add: Reinsurance recoverables	4	5
Add: Impact of discount rate on long-duration insurance reserves	(26)	5
Health care costs payable, end of the period	12,550	10,131
Premium deficiency reserve	$ 0	$ 5