BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	$ 8,143
Reinsurance recoverable on unpaid claims	0	$ 68	$ 95	$ 70
Total benefits payable, gross	8,143	6,004	4,862	4,668
Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	7,428
Reinsurance recoverable on unpaid claims	0	68	95	70
Total benefits payable, gross	7,428	5,363	4,338	3,963
Group and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	715
Total benefits payable, gross	$ 715	$ 641	$ 517	$ 568