INVESTMENTS - Other Invested Assets (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	$ 409	$ 211
Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	147	85
Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	262	126
Partnership Interest | Fair Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	35	33
Partnership Interest | Fair Value | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	29	24
Partnership Interest | Fair Value | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	6	9
Private equity | Partnership Interest | Fair Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	29	24
Private equity | Partnership Interest | Fair Value | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	29	24
Private equity | Partnership Interest | Fair Value | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	0	0
Derivative instruments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	282	117
Derivative instruments | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	26	0
Derivative instruments | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	256	117
Other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	92	61
Other | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	92	61
Other | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	0	0
Equity Method Investments | Partnership Interest
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	6	9
Equity Method Investments | Partnership Interest | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	0	0
Equity Method Investments | Partnership Interest | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	6	9
Equity Method Investments | Private equity | Partnership Interest
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	3	4
Equity Method Investments | Private equity | Partnership Interest | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	0	0
Equity Method Investments | Private equity | Partnership Interest | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	3	4
Equity Method Investments | Real estate-related | Partnership Interest
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	3	5
Equity Method Investments | Real estate-related | Partnership Interest | Retained Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	0	0
Equity Method Investments | Real estate-related | Partnership Interest | Ceded Business
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other invested assets	$ 3	$ 5