BENEFITS PAYABLE - Activity in Benefits Payable (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	$ 4,668	$ 4,563
Less: Reinsurance recoverables	(70)	(76)
Balances, beginning of period, net	4,598	4,487
Incurred related to:
Current year	23,543	22,576
Prior years	(338)	(345)
Total incurred	23,205	22,231
Paid related to:
Current year	(18,914)	(18,332)
Prior years	(3,897)	(3,626)
Total paid	(22,811)	(21,958)
Reinsurance recoverable	86	78
Balances, end of period	5,020	4,838
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	3,963	3,507
Less: Reinsurance recoverables	(70)	(76)
Balances, beginning of period, net	3,893	3,431
Incurred related to:
Current year	21,069	20,010
Prior years	(247)	(287)
Total incurred	20,822	19,723
Paid related to:
Current year	(17,061)	(16,385)
Prior years	(3,327)	(2,707)
Total paid	(20,388)	(19,092)
Reinsurance recoverable	86	78
Balances, end of period	4,413	4,140
Total IBNR	2,900
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	568	578
Incurred related to:
Current year	2,665	2,629
Prior years	(34)	(31)
Total incurred	2,631	2,598
Paid related to:
Current year	(2,094)	(2,117)
Prior years	(496)	(518)
Total paid	(2,590)	(2,635)
Balances, end of period	609	541
Total IBNR	530
Individual Commercial
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	101	454
Incurred related to:
Current year	0	304
Prior years	(55)	(26)
Total incurred	(55)	278
Paid related to:
Current year	0	(223)
Prior years	(31)	(378)
Total paid	(31)	(601)
Balances, end of period	15	131
Total IBNR	6
Disposal Group, Held-for-sale, Not Discontinued Operations
Paid related to:
Less: Held-for-sale	$ (58)	$ 0