FAIR VALUE OF ASSETS AND LIABILITIES - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets
Accrued investment income	$ 65	$ 60
Fair Value | Fair Value, Inputs, Level 1, Level 2, and Level 3
Assets
Accrued investment income	65	60
Mortgage loans	92	61
Liabilities:
Repurchase agreements	1,000	825
Securities lending transactions	2
Fair Value | Level 1
Assets
Accrued investment income	0	0
Mortgage loans	81	50
Liabilities:
Repurchase agreements	0	0
Securities lending transactions	0
Fair Value | Level 2
Assets
Accrued investment income	65	60
Mortgage loans	0	0
Liabilities:
Repurchase agreements	1,000	825
Securities lending transactions	2
Fair Value | Level 3
Assets
Accrued investment income	0	0
Mortgage loans	11	11
Liabilities:
Repurchase agreements	0	0
Securities lending transactions	0
Carrying Amount
Assets
Accrued investment income	65	60
Mortgage loans	92	61
Liabilities:
Repurchase agreements	1,121	$ 967
Securities lending transactions	$ 2