Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amortization of deferred policy acquisition costs	$ 478	$ 502	$ 483
Pharmacy Benefits Management Services | Performance Guarantee
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Performance guarantee liability	1,100	1,100
Administrative Services Only Health Care Services | Performance Guarantee
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loss contingency accrual provision
Amounts paid for loss contigency