HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended		11 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Nov. 02, 2017
Supplementary Insurance Information, by Segment [Line Items]
Premium deficiency reserve		$ 176
Premium deficiency reserve, change in estimate				$ 208
Policyholder benefits and claims incurred, net, health, increase				$ 208
Write off of risk corridor receivables		583
Other current assets		3,438			$ 3,776		$ 3,776
Trade accounts payable and accrued expenses		(2,467)			(4,888)		(4,888)
Other long-term assets		2,226			2,214		2,214
Other long-term liabilities		(263)			(457)		(457)
Subsequent Event
Supplementary Insurance Information, by Segment [Line Items]
Litigation recoveries sought								$ 611
Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		196			129		129
Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		260			44		44
Health Care Reform
Supplementary Insurance Information, by Segment [Line Items]
Payment of annual health insurance industry fee	$ 916
Amortization of deferred charges			$ 231			$ 687
2014 and 2015 Coverage Years
Supplementary Insurance Information, by Segment [Line Items]
Write off of risk corridor receivables		415
2014 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Risk corridor received since inception							39
Prior Coverage Years
Supplementary Insurance Information, by Segment [Line Items]
Proceeds from reinsurance recoverable					283	471
Proceeds from risk adjustment settlements and risk corridor					176	88
Payments For Risk Adjustment Charges					152	$ 240
Prior Coverage Years | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		307			127		127
Other current assets		0			0		0
Trade accounts payable and accrued expenses		(117)			0		0
Net current (liability) asset		190			127		127
Other long-term assets		6			0		0
Total net (liability) asset		196			127		127
Prior Coverage Years | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0			0		0
Other current assets		260			44		44
Trade accounts payable and accrued expenses		0			0		0
Net current (liability) asset		260			44		44
Other long-term assets		0			0		0
Total net (liability) asset		260			44		44
Current Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0			30		30
Trade accounts payable and accrued expenses		0			(57)		(57)
Net current (liability) asset		0			(27)		(27)
Other long-term assets		0			29		29
Other long-term liabilities		0			0		0
Net long-term asset (liability)		0			29		29
Total net (liability) asset		0			2		2
Current Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0			0		0
Trade accounts payable and accrued expenses		0			0		0
Net current (liability) asset		0			0		0
Other long-term assets		0			0		0
Other long-term liabilities		0			0		0
Net long-term asset (liability)		0			0		0
Total net (liability) asset		$ 0			$ 0		$ 0