COMPREHENSIVE INCOME (LOSS) - Schedule of Reclassification from Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized capital gains (losses)	$ (180)	$ (982)	$ 501
Income tax expense (benefit)	210	(112)	192
Other underwriting expenses	574	501	454
Net income (loss)	972	(445)	$ 800
URA(D) on securities - temporary | Reclassification From Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized capital gains (losses)	193	93
Income tax expense (benefit)	(41)	(20)
Net income (loss)	153	73
Benefit plan net gain (loss) | Reclassification From Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	(1)
Other underwriting expenses	2	3
Net income (loss)	$ 2	$ 2