HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Jun. 30, 2018	Jun. 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		$ 4,410	$ 4,410		$ 2,949
Trade accounts payable and accrued expenses		(6,952)	(6,952)		(4,069)
Other long-term assets		1,506	1,506		2,166
Other long-term liabilities		(321)	(321)		(237)
Health Care Reform
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Amortization of deferred charges		257	520
Prior Coverage Years
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Proceeds from risk corridor settlements			46	$ 64
Forecast | Health Care Reform
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]
Total net (liability) asset		(64)	(64)		(13)
Risk Adjustment Settlement | Prior Coverage Years
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums receivable		65	65		62
Other current assets		0	0		0
Trade accounts payable and accrued expenses		(103)	(103)		(80)
Other long-term assets		1	1		5
Risk Adjustment Settlement | Current Coverage Year
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Other long-term liabilities		(27)	(27)		0
Reinsurance Recoverables
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Total net (liability) asset		0	0		44
Reinsurance Recoverables | Prior Coverage Years
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
Reinsurance Recoverables | Current Coverage Year
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Other long-term liabilities		$ 0	$ 0		$ 0