RELATED PARTY TRANSACTIONS - Successor Company (Details) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Nov. 30, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2021	Apr. 01, 2022
Related Party Transaction [Line Items]
Net investment income		$ 99,000,000	$ 255,000,000	$ 315,000,000	$ 490,000,000
Funding commitment				135,000,000
Fortitude Group Holdings
Related Party Transaction [Line Items]
Allocation of costs			23,000,000	30,000,000
Intercompany liquidity agreement, maximum borrowing capacity				300,000,000
Intercompany liquidity agreement, amount borrowed				434,000,000
Intercompany liquidity agreement, loaned	$ 150,000,000
Fortitude Group Holdings | Intercompany Liquidity Agreement, Transaction One
Related Party Transaction [Line Items]
Intercompany liquidity agreement, amount borrowed			75,000,000
Fortitude Group Holdings | Intercompany Liquidity Agreement, Transaction Two
Related Party Transaction [Line Items]
Intercompany liquidity agreement, amount borrowed			75,000,000
Carlyle Investment Management L.L.C.
Related Party Transaction [Line Items]
Assets under management, market value			732,000,000	529,000,000
Net investment income			9,000,000	29,000,000
Carlyle Investment Management L.L.C. | Consulting Services
Related Party Transaction [Line Items]
Transaction costs			10,000,000
Carlyle Investment Management L.L.C. | Investment Management Services
Related Party Transaction [Line Items]
Transaction costs			$ 0	$ 5,000,000
Fortitude Group Holdings | Carlyle Investment Management L.L.C.
Related Party Transaction [Line Items]
Ownership						38.53%