HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 01, 2015
Supplementary Insurance Information, by Segment [Line Items]
Provision for premium deficiency		$ 176	$ 176	$ 0	$ 0
Future policy benefits payable		2,151	2,151	2,349
Other current assets		4,712	4,712	4,007
Trade accounts payable and accrued expenses		(2,212)	(2,212)	(2,095)
Other long-term assets		2,502	2,502	1,583
Other long-term liabilities		(235)	(235)	(236)
Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		(87)	(87)	42
Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		610	610	586
Risk Corridor Settlement
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		459	459	51
2014 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Risk adjustment charges			(186)
Payment for risk corridor charges			(1)
Proceeds from reinsurance recoverable			521
Proceeds from risk corridor settlements			26
2014 Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Proceeds from legal settlements			57
Premiums receivable		4	4	131
Other current assets		0	0	0
Trade accounts payable and accrued expenses		0	0	(89)
Net current (liability) asset		4	4	42
Other long-term assets		0	0	0
Other long-term liabilities		0	0	0
Net long-term asset		0	0	0
Total net (liability) asset		4	4	42
2014 Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0	0	0
Other current assets		0	0	586
Trade accounts payable and accrued expenses		0	0	0
Net current (liability) asset		0	0	586
Other long-term assets		0	0	0
Other long-term liabilities		0	0	0
Net long-term asset		0	0	0
Total net (liability) asset		0	0	586
2014 Coverage Year | Risk Corridor Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable to be paid by CMS, percent (to be paid between December 2015 and January 2016)						12.60%
Premiums receivable		0	0	0
Other current assets		0	0	55
Trade accounts payable and accrued expenses		0	0	(4)
Net current (liability) asset		0	0	51
Other long-term assets		215	215	0
Other long-term liabilities		0	0	0
Net long-term asset		215	215	0
Total net (liability) asset		215	215	51
2015 Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		122	122	0
Other current assets		0	0	0
Trade accounts payable and accrued expenses		(223)	(223)	0
Net current (liability) asset		(101)	(101)	0
Other long-term assets		10	10	0
Other long-term liabilities		0	0	0
Net long-term asset		10	10	0
Total net (liability) asset		(91)	(91)	0
2015 Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0	0	0
Other current assets		610	610	0
Trade accounts payable and accrued expenses		0	0	0
Net current (liability) asset		610	610	0
Other long-term assets		0	0	0
Other long-term liabilities		0	0	0
Net long-term asset		0	0	0
Total net (liability) asset		610	610	0
2015 Coverage Year | Risk Corridor Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0	0	0
Other current assets		0	0	0
Trade accounts payable and accrued expenses		0	0	0
Net current (liability) asset		0	0	0
Other long-term assets		244	244	0
Other long-term liabilities		0	0	0
Net long-term asset		244	244	0
Total net (liability) asset		244	244	0
2016 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Provision for premium deficiency		176
Future policy benefits payable		$ 340	340
Health Care Reform
Supplementary Insurance Information, by Segment [Line Items]
Decline in the estimated net receivable			$ (43)
Payment of annual health insurance industry fee	$ 867			$ 562