BENEFITS PAYABLE - Activity in Benefits Payable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	$ 8,143	$ 6,004	$ 4,862
Less: Reinsurance recoverables	0	(68)	(95)
Balances, beginning of period, net	8,143	5,936	4,767
Acquisitions	42	0	0
Incurred related to:
Current year	70,024	61,941	54,193
Prior years	(825)	(313)	(336)
Total incurred	69,199	61,628	53,857
Paid related to:
Current year	(62,149)	(54,003)	(48,421)
Prior years	(6,946)	(5,418)	(4,267)
Total paid	(69,095)	(59,421)	(52,688)
Reinsurance recoverable	0	0	68
Balances, end of period	8,289	8,143	6,004
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	7,428	5,363	4,338
Less: Reinsurance recoverables	0	(68)	(95)
Balances, beginning of period, net	7,428	5,295	4,243
Acquisitions	42	0	0
Incurred related to:
Current year	65,636	56,821	48,983
Prior years	(729)	(266)	(386)
Total incurred	64,907	56,555	48,597
Paid related to:
Current year	(58,363)	(49,586)	(43,831)
Prior years	(6,339)	(4,836)	(3,714)
Total paid	(64,702)	(54,422)	(47,545)
Reinsurance recoverable	0	0	68
Balances, end of period	7,675	7,428	5,363
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	715	641	517
Incurred related to:
Current year	5,047	5,576	5,708
Prior years	(96)	(47)	50
Total incurred	4,951	5,529	5,758
Paid related to:
Current year	(4,445)	(4,873)	(5,081)
Prior years	(607)	(582)	(553)
Total paid	(5,052)	(5,455)	(5,634)
Balances, end of period	$ 614	$ 715	$ 641