Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule of Premium Revenue by Health Plan Type [Line Items]
Risk adjustment payable	$ (949)		$ 902
Risk adjustment receivable	33		7
Risk adjustment, net payable	$ 916		$ 895
Maturity period (less than)	15 years
Structured Securities
Schedule of Premium Revenue by Health Plan Type [Line Items]
Average maturity period (less than)	15 years
COVID-19
Schedule of Premium Revenue by Health Plan Type [Line Items]
Reduction in premiums	$ 28	$ 110