Statutory Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Statutory risk-based capital necessary to satisfy regulatory requirements	$ 5,800				$ 5,500				$ 5,800	$ 5,500
GAAP equity	33,199				31,728				33,199	31,728	$ 28,541	$ 26,503
Net income	551	$ 222	$ 2,276	$ 1,523	934	$ 1,183	$ 1,139	$ 1,551	4,572	4,807	3,750
California Department of Managed Health Care [Member]
Statutory Accounting Practices [Line Items]
Statutory risk-based capital necessary to satisfy regulatory requirements	600				610				600	610
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	13,717				13,044				13,717	13,044
Statutory-basis net income									3,170	3,840	3,412
California Department of Managed Health Care Regulated Entities [Member]
Statutory Accounting Practices [Line Items]
GAAP equity	$ 3,851				$ 3,359				3,851	3,359
Net income									$ 753	$ 878	$ 789