BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 7,977
Reinsurance recoverable on unpaid claims	3	$ 68	$ 72	$ 95
Benefits payable	7,980	6,004	5,842	4,862
Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Reinsurance recoverable on unpaid claims	3	68	72	95
Benefits payable	7,423	5,363	5,243	4,338
Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	557	$ 641	$ 599	$ 517
Operating Segments | Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	7,420
Reinsurance recoverable on unpaid claims	3
Operating Segments | Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 557