HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Nov. 02, 2017
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Litigation recoveries sought						$ 611
Other current assets		$ 4,178	$ 4,178		$ 2,949
Trade accounts payable and accrued expenses		(5,413)	(5,413)		(4,069)
Other long-term assets		1,380	1,380		2,166
Payments for risk corridor settlements			(60)
Proceeds from risk corridor settlements				$ 307
Health Care Reform
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Amortization of deferred charges		258	778
Health Care Reform | Subsequent Event
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Payment of annual health insurance industry fee	$ 1,040
Risk Adjustment Settlement
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums receivable		68	68		62
Other current assets		0	0		0
Trade accounts payable and accrued expenses		(40)	(40)		(80)
Other long-term assets		0	0		5
Total net asset (liability)		28	28		(13)
Reinsurance Recoverables
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums receivable		0	0		0
Other current assets		0	0		44
Trade accounts payable and accrued expenses		0	0		0
Other long-term assets		0	0		0
Total net asset (liability)		$ 0	$ 0		$ 44