BENEFITS PAYABLE - Activity in Benefits Payable (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balances at January 1	$ 4,668	$ 4,563	$ 4,976
Less: Premium deficiency reserve	0	0	(176)
Less: Reinsurance recoverables	(70)	(76)	(85)
Balances at January 1, net		4,598	4,487	$ 4,715
Current year, Incurred	46,385	44,001	45,318
Prior years, Incurred	(503)	(483)	(582)
Total incurred	45,882	43,518	44,736
Current year, Paid	(41,736)	(39,496)	(40,852)
Prior years, Paid	(3,977)	(3,911)	(4,112)
Total paid	(45,713)	(43,407)	(44,964)
Reinsurance recoverable	95	70	76
Balances at December 31	4,862	4,668	4,563
Retail
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balances at January 1	3,963	3,506	3,600
Less: Reinsurance recoverables	(70)	(76)	(85)
Balances at January 1, net		3,893	3,430	3,515
Current year, Incurred	41,323	38,604	37,212
Prior years, Incurred	(398)	(386)	(429)
Total incurred	40,925	38,218	36,783
Current year, Paid	(37,189)	(34,781)	(33,784)
Prior years, Paid	(3,386)	(2,974)	(3,084)
Total paid	(40,575)	(37,755)	(36,868)
Reinsurance recoverable	95	70	76
Balances at December 31	4,338	3,963	3,506
Group and Specialty
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balances at January 1	568	579	616
Less: Reinsurance recoverables	0	0	0
Balances at January 1, net		568	579	616
Current year, Incurred	5,466	5,403	5,271
Prior years, Incurred	(46)	(40)	(46)
Total incurred	5,420	5,363	5,225
Current year, Paid	(4,957)	(4,843)	(4,700)
Prior years, Paid	(514)	(531)	(562)
Total paid	(5,471)	(5,374)	(5,262)
Reinsurance recoverable		0	0
Balances at December 31	517	568	579
Individual Commercial
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balances at January 1	101	454	741
Less: Premium deficiency reserve	0	0	(176)
Balances at January 1, net		101	454	$ 565
Current year, Incurred	0	669	3,677
Prior years, Incurred	(56)	(56)	(106)
Total incurred	(56)	613	3,571
Current year, Paid	0	(583)	(3,233)
Prior years, Paid	(38)	(383)	(449)
Total paid	(38)	(966)	(3,682)
Balances at December 31	$ 7	$ 101	$ 454

Health Care Reform, Provision for Premium Deficiency

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The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

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Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs.

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Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs.

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Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred and costs incurred in the claim settlement process.

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Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer.

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