RELATED-PARTY TRANSACTIONS - Premiums and Losses Ceded by the Company to Affiliate (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Mt. Logan Re Segregated Accounts
Effects of Reinsurance [Line Items]
Ceded written premiums	$ 40	$ 22	$ 82	$ 62
Ceded earned premiums	44	29	82	72
Ceded losses and LAE	19	23	32	60
Bermuda Re
Effects of Reinsurance [Line Items]
Ceded written premiums	107	91	214	184
Ceded earned premiums	107	91	213	184
Ceded losses and LAE	(5)	3	(9)	1
Assumed written premiums	4	1	4	3
Assumed earned premiums	3	1	3	5
Assumed losses and LAE	0	0	0	0
Ireland Re
Effects of Reinsurance [Line Items]
Assumed written premiums	3	2	6	4
Assumed earned premiums	3	2	6	5
Assumed losses and LAE	1	0	1	2
Ireland Insurance
Effects of Reinsurance [Line Items]
Assumed written premiums	11	2	12	4
Assumed earned premiums	8	2	10	4
Assumed losses and LAE	$ 2	$ (5)	$ 4	$ 2