FAIR VALUE DISCLOSURES - Fair Value Measurement Reconciliation For All Levels (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Total Gains (Losses), Realized And Unrealized Included In Net Income (Loss) [Abstract]
Net derivative gains (losses)	$ (7,000,000)	$ (8,000,000)	$ 4,000,000
Transfers into Level 3	0	0
Transfers out of Level 3	(10,000,000)	(5,000,000)
Level 3 | Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	18,000,000	11,000,000	14,000,000
Total Gains (Losses), Realized And Unrealized Included In Net Income (Loss) [Abstract]
Investment gains (losses), reported in net investment income	0	0	0
Net derivative gains (losses)	0	0	0
Total realized and unrealized gains (losses)	0	0	0
Other comprehensive income (loss)	1,000,000	(1,000,000)	0
Purchases	79,000,000	14,000,000	1,000,000
Sales	(1,000,000)	(1,000,000)	(4,000,000)
Change in fair value of funds withheld assets	0		0
Transfers into Level 3	0	0	0
Transfers out of Level 3	(10,000,000)	(5,000,000)	0
Closing Balance	87,000,000	18,000,000	11,000,000
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period	0	0	0
Change in unrealized gains or losses for the period included in other comprehensive income for instruments held at the end of the reporting period.	1,000,000	(1,000,000)	0
Level 3 | Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	0	0
Total Gains (Losses), Realized And Unrealized Included In Net Income (Loss) [Abstract]
Investment gains (losses), reported in net investment income	0	0	0
Net derivative gains (losses)	0	0	0
Total realized and unrealized gains (losses)	0	0	0
Other comprehensive income (loss)	0	0	0
Purchases	32,000,000	0	0
Sales	(8,000,000)	0	0
Change in fair value of funds withheld assets			0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Closing Balance	24,000,000	0	0
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period	0	0	0
Change in unrealized gains or losses for the period included in other comprehensive income for instruments held at the end of the reporting period.	0	0	0
Level 3 | Commercial mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	0	0
Total Gains (Losses), Realized And Unrealized Included In Net Income (Loss) [Abstract]
Investment gains (losses), reported in net investment income	0	0	0
Net derivative gains (losses)	0	0	0
Total realized and unrealized gains (losses)	0	0	0
Other comprehensive income (loss)	0	0	0
Purchases	1,000,000	0	0
Sales	0	0	0
Change in fair value of funds withheld assets	0		0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Closing Balance	1,000,000	0	0
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period	0	0	0
Change in unrealized gains or losses for the period included in other comprehensive income for instruments held at the end of the reporting period.	0	0	0
Level 3 | Funds Withheld Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	0	0
Total Gains (Losses), Realized And Unrealized Included In Net Income (Loss) [Abstract]
Investment gains (losses), reported in net investment income	0	0	0
Net derivative gains (losses)	0	0	0
Total realized and unrealized gains (losses)	0	0	0
Other comprehensive income (loss)	0	0	0
Purchases	0	0	0
Sales	0	0	0
Change in fair value of funds withheld assets	100,000,000		0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Closing Balance	100,000,000	0	0
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period	0	0	0
Change in unrealized gains or losses for the period included in other comprehensive income for instruments held at the end of the reporting period.	0	0	0
Level 3 | Modco Receivable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	0	0
Total Gains (Losses), Realized And Unrealized Included In Net Income (Loss) [Abstract]
Investment gains (losses), reported in net investment income	0	0	0
Net derivative gains (losses)	0	0	0
Total realized and unrealized gains (losses)	0	0	0
Other comprehensive income (loss)	0	0	0
Purchases	0	0	0
Sales	0	0	0
Change in fair value of funds withheld assets	(411,000,000)		0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Closing Balance	(411,000,000)	0	0
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period	0	0	0
Change in unrealized gains or losses for the period included in other comprehensive income for instruments held at the end of the reporting period.	$ 0	$ 0	$ 0