FAIR VALUE DISCLOSURES - Fair Value Measurement Reconciliation For All Levels (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Total gains and (losses), realized and unrealized, included in:
Transfers into Level 3	$ 27	$ 11
Transfers out of Level 3	(109)	(352)
Level 3 | Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,070	2,103	$ 1,493
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	7	6	5
Investment gains (losses), net	(4)	(17)	(5)
Subtotal	3	(11)	0
Other comprehensive income (loss)	18	50	(157)
Purchases	548	514	1,093
Sales	(547)	(272)	(379)
Activity related to consolidated VIEs/VOEs	0	0	0
Transfers into Level 3	27	11	168
Transfers out of Level 3	(68)	(325)	(115)
Balance, end of period	2,051	2,070	2,103
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	17	4	(154)
Level 3 | State and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	27	29	35
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	0	0	0
Investment gains (losses), net	0	0	0
Subtotal	0	0	0
Other comprehensive income (loss)	0	0	(5)
Purchases	0	0	0
Sales	0	(2)	(1)
Activity related to consolidated VIEs/VOEs	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	(27)	0	0
Balance, end of period	0	27	29
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	(5)
Level 3 | Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	24	0	8
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	0	0	0
Investment gains (losses), net	0	0	0
Subtotal	0	0	0
Other comprehensive income (loss)	0	0	0
Purchases	0	24	0
Sales	0	0	(2)
Activity related to consolidated VIEs/VOEs	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	(14)	0	(6)
Balance, end of period	10	24	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 | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	6	32	20
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	0	0	0
Investment gains (losses), net	0	0	0
Subtotal	0	0	0
Other comprehensive income (loss)	0	(1)	(2)
Purchases	0	2	14
Sales	0	0	0
Activity related to consolidated VIEs/VOEs	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	(27)	0
Balance, end of period	6	6	32
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	(1)	(2)
Level 3 | Other equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	57	17	13
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	1	(2)	(1)
Investment gains (losses), net	0	0	0
Subtotal	1	(2)	(1)
Other comprehensive income (loss)	0	0	0
Purchases	0	43	8
Sales	(2)	0	0
Change in fair value of funds withheld assets	0	0
Other	0		0
Activity related to consolidated VIEs/VOEs	(1)	(1)	(3)
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Balance, end of period	55	57	17
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period	1	(2)	(1)
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 | Separate Accounts Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	1	1
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income		0	0
Investment gains (losses), net		0	0
Subtotal		0	0
Other comprehensive income (loss)		0	0
Purchases		0	0
Sales		0	0
Change in fair value of funds withheld assets		0
Other			0
Activity related to consolidated VIEs/VOEs		0	0
Transfers into Level 3		0	0
Transfers out of Level 3		(1)	0
Balance, end of period		0	1
Change in unrealized gains or losses for the period included in earnings for instruments held at the end of the reporting period		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
Level 3 | Funds Withheld Payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	100	0	0
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	0	0	0
Investment gains (losses), net	0	0	0
Subtotal	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	50	100
Other	0		0
Activity related to consolidated VIEs/VOEs	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Balance, end of period	150	100	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 Payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	(411)	0	0
Total gains and (losses), realized and unrealized, included in:
Investment gains (losses), reported in net investment income	0	0	0
Investment gains (losses), net	0	0	0
Subtotal	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	66	(411)
Other	0		0
Activity related to consolidated VIEs/VOEs	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Balance, end of period	(345)	(411)	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