Health Care Costs Payable - Reconciliation of Health Care Costs Payable (Details) - USD ($) $ in Millions		12 Months Ended
	Nov. 28, 2018	Dec. 31, 2019	Dec. 31, 2018
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Health care costs payable, beginning of the period		$ 6,147
Reclassification from pharmacy claims and discounts payable	$ 776
Less: Claims paid
Health care costs payable, end of period		6,879	$ 6,147
Health Care Benefits
Less: Claims paid
Amounts excluded from total incurred health care costs		41	4
Corporate/ Other
Less: Claims paid
Amounts excluded from total incurred health care costs		285	22
Health Insurance Product Line
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Health care costs payable, beginning of the period		6,147	5
Less: Reinsurance recoverables		4	0
Health care costs payable, beginning of the period		6,143	5
Acquisitions, net		0	5,357
Reclassification from pharmacy claims and discounts payable		0	776
Add: Components of incurred health care costs
Current year		52,723	6,594
Prior years		(524)	(42)
Total incurred health care costs		52,199	6,552
Less: Claims paid
Current year		46,158	6,303
Prior years		5,314	260
Total claims paid		51,472	6,563
Add: Premium deficiency reserve		4	16
Health care costs payable, end of period		6,874	6,143
Add: Reinsurance recoverables		5	4
Health care costs payable, end of period		$ 6,879	$ 6,147