Health Care Costs Payable - Incurred and Paid Health Care Claims Development (Details) - Health Insurance Product Line - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Claims Development [Line Items]
Incurred Health Care Claims,Net of Reinsurance	$ 105,585
Cumulative Paid Health Care Claims,Net of Reinsurance	97,961
All outstanding liabilities for health care costs payable prior to 2019, net of reinsurance	144
Total outstanding liabilities for health care costs payable, net of reinsurance	7,768
2019
Claims Development [Line Items]
Incurred Health Care Claims,Net of Reinsurance	51,056	$ 51,426
Cumulative Paid Health Care Claims,Net of Reinsurance	50,394	$ 44,987
2020
Claims Development [Line Items]
Incurred Health Care Claims,Net of Reinsurance	54,529
Cumulative Paid Health Care Claims,Net of Reinsurance	$ 47,567