FAIR VALUE - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2015	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value		$ 16,085,000,000	$ 15,932,000,000
Annual dividend rate	1.75%
Transfers in/(out) of Level 3 and reclassification of securities in/(out) of investment categories		0
Other invested assets, at fair value		1,478,000,000	1,481,000,000
Fair Value | Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other invested assets, at fair value		$ 258,000,000	274,000,000
4.868% Senior notes | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Observable input constant maturity		10 years
Other invested assets, at fair value		4.868%
Redeemable Convertible Preferred Stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Preferred stock term		25 years
Annual dividend rate		1.75%
Fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value		$ 2,000,000,000	$ 2,000,000,000