Health Care Costs Payable (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Health care costs payable, beginning of the period, net	$ 6,147
Less: Claims paid
Health care costs payable, end of period, net	6,889
Decrease in prior year health care costs payable	(489)
Incurred but not reported (IBNR) claims liability, net	5,100
Health Insurance Product Line
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Health care costs payable, beginning of the period	6,147
Less: Reinsurance recoverables	4
Health care costs payable, beginning of the period, net	6,143
Add: Components of incurred health care costs
Current year	26,864
Prior years	(489)
Total incurred health care costs	26,375
Less: Claims paid
Current year	20,552
Prior years	5,095
Total claims paid	25,647
Add: Premium deficiency reserve	14
Health care costs payable, end of period, net	6,885
Add: Reinsurance recoverables	4
Health care costs payable, end of period	6,889
Premium deficiency reserve	14
Health Care Benefits Segment
Less: Claims paid
Benefit costs recorded in other insurance liabilities	21
Corporate / Other
Less: Claims paid
Benefit costs recorded in other insurance liabilities	$ 136