BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	$ 5,936
Reinsurance recoverable on unpaid claims	68	$ 95	$ 70	$ 76
Total benefits payable, gross	6,004	4,862	4,668	4,563
Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	5,295
Reinsurance recoverable on unpaid claims	68	95	70	76
Total benefits payable, gross	5,363	4,338	3,963	3,506
Group and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	641
Total benefits payable, gross	641	$ 517	$ 568	$ 579
Operating Segments | Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
Reinsurance recoverable on unpaid claims	$ 68