10-K Statutory Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2021
Statutory Accounting Practices [Line Items]
Statutory risk-based capital necessary to satisfy regulatory requirements	$ 7,900			$ 6,962
Total Shareholders' Balance, beginning	36,243	$ 38,423	$ 36,055	36,095
Statutory Accounting Practices, Dividends Paid with Approval of Regulatory Agency	3,097
Estimated Future Dividend Payments	3,500
California Department of Managed Health Care [Member]
Statutory Accounting Practices [Line Items]
Statutory risk-based capital necessary to satisfy regulatory requirements	710			690
Insurance, HMO Subsidiaries and Other Regulated Entities, Excluding the California Department of Managed Health Care [Member]
Statutory Accounting Practices [Line Items]
Statutory-basis capital and surplus	19,048			16,178
California Department of Managed Health Care Regulated Entities [Member]
Statutory Accounting Practices [Line Items]
Total Shareholders' Balance, beginning	$ 3,795			$ 3,886