HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Supplementary Insurance Information, by Segment [Line Items]
Premium deficiency reserve		$ 176			$ 0		$ 176
Premium deficiency reserve, change in estimate			$ 208	$ 13
Policyholder benefits and claims incurred, net, health, increase			208
Write off of risk corridor receivables		583
Other current assets		3,438			3,884		3,438
Trade accounts payable and accrued expenses		(2,467)			(4,693)		(2,467)
Other long-term assets		2,226			2,192		2,226
Other long-term liabilities		(263)			(417)		(263)
Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		196			143		196
Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		260			268		260
Health Care Reform
Supplementary Insurance Information, by Segment [Line Items]
Payment of annual health insurance industry fee	$ 916
Amortization of deferred charges			$ 229			$ 456
2014 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Increase (decrease) in premiums receivable							(38)
2015 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Proceeds from reinsurance recoverable					60	214
Proceeds from risk adjustment settlements					3	$ 8
2014 and 2015 ACA Products
Supplementary Insurance Information, by Segment [Line Items]
Write off of risk corridor receivables		415
2016 Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		307			291		307
Other current assets		0			0		0
Trade accounts payable and accrued expenses		(117)			(150)		(117)
Net current asset		190			141		190
Other long-term assets		6			0		6
Total net (liability) asset		196			141		196
2016 Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0			0		0
Other current assets		260			268		260
Trade accounts payable and accrued expenses		0			0		0
Net current asset		260			268		260
Other long-term assets		0			0		0
Total net (liability) asset		260			268		260
Current Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0			12		0
Net current asset		0			12		0
Other long-term assets		0			30		0
Other long-term liabilities		0			(40)		0
Net long-term liability		0			(10)		0
Total net (liability) asset		0			2		0
Current Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0			0		0
Net current asset		0			0		0
Other long-term assets		0			0		0
Other long-term liabilities		0			0		0
Net long-term liability		0			0		0
Total net (liability) asset		$ 0			$ 0		$ 0