Health Care Costs Payable - Incurred and Paid Health Care Claims Development (Details) - Health Insurance Product Line - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Claims Development [Line Items]
Incurred Health Care Claims,Net of Reinsurance	$ 96,047
Cumulative Paid Health Care Claims,Net of Reinsurance	89,360
All outstanding liabilities for health care costs payable prior to 2018, net of reinsurance	56
Total outstanding liabilities for health care costs payable, net of reinsurance	6,743
2018
Claims Development [Line Items]
Incurred Health Care Claims,Net of Reinsurance	44,621	$ 44,962
Cumulative Paid Health Care Claims,Net of Reinsurance	44,373	$ 39,440
2019
Claims Development [Line Items]
Incurred Health Care Claims,Net of Reinsurance	51,426
Cumulative Paid Health Care Claims,Net of Reinsurance	$ 44,987