BENEFITS PAYABLE - Incurred and Paid Claims Development (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	$ 170,614
Cumulative Paid Claims, Net of Reinsurance	162,939
Benefits payable, net of reinsurance	7,675
Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	16,190
Cumulative Paid Claims, Net of Reinsurance	15,576
Benefits payable, net of reinsurance	614
2019 Claims Incurred Year | Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	48,713	$ 48,820	$ 48,983
Cumulative Paid Claims, Net of Reinsurance	48,713	48,627	43,831
2019 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	5,652	5,657	5,708
Cumulative Paid Claims, Net of Reinsurance	5,652	5,465	$ 5,081
2020 Claims Incurred Year | Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	56,223	56,821
Cumulative Paid Claims, Net of Reinsurance	55,863	49,586
2020 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	5,491	5,576
Cumulative Paid Claims, Net of Reinsurance	5,479	$ 4,873
2021 Claims Incurred Year | Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	65,678
Cumulative Paid Claims, Net of Reinsurance	58,363
2021 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	5,047
Cumulative Paid Claims, Net of Reinsurance	$ 4,445