Medical Claims Liability - Incurred Claims and Allocated Claims Adjustment Expenses (Details) - Health insurance product line claims in Millions, $ in Millions	Dec. 31, 2021 USD ($) claims	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Claims Development [Line Items]
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net	$ 270,137
2019
Claims Development [Line Items]
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net	83,250	$ 83,329	$ 84,027
Short-duration insurance contracts, expected development on reported claims	$ 3
Short-duration Insurance contracts, number of reported claims | claims	516.2
2020
Claims Development [Line Items]
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net	$ 86,502	$ 88,206
Short-duration insurance contracts, expected development on reported claims	$ 92
Short-duration Insurance contracts, number of reported claims | claims	568.2
2021
Claims Development [Line Items]
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net	$ 100,385
Short-duration insurance contracts, expected development on reported claims	$ 9,544
Short-duration Insurance contracts, number of reported claims | claims	597.3