INVESTMENTS - Summary of Contractual Maturities of Fixed Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Amortized cost
Due in one year or less	$ 422,039	$ 503,716
Due after one year through five years	5,349,123	4,878,151
Due after five years through ten years	2,192,344	2,478,542
Due after ten years	234,046	277,756
Total fixed maturities with a single maturity date (amortized cost)	8,197,552	8,138,165
Amortized cost	12,176,473	12,241,782
Fair value
Due in one year or less	409,972	505,602
Due after one year through five years	5,078,273	4,908,640
Due after five years through ten years	1,919,450	2,488,478
Due after ten years	205,575	279,056
Total fixed maturities with a single maturity date (fair value)	7,613,270	8,181,776
Fair value	$ 11,326,894	$ 12,313,200
% of Total fair value
Due in one year or less	3.70%	4.10%
Due after one year through five years	44.80%	39.90%
Due after five years through ten years	16.90%	20.20%
Due after ten years	1.80%	2.30%
Fixed maturities with a single maturity date (% of total fair value)	67.20%	66.50%
Total	100.00%	100.00%
Agency RMBS
Amortized cost
Fixed maturities without a single maturity date	$ 1,297,423	$ 1,065,973
Amortized cost	1,297,423	1,065,973
Fair value
Fixed maturities without a single maturity date (fair value)	1,202,785	1,074,589
Fair value	$ 1,202,785	$ 1,074,589
% of Total fair value
Fixed maturities without a single maturity date (% of total fair value)	10.60%	8.70%
CMBS
Amortized cost
Fixed maturities without a single maturity date	$ 1,029,863	$ 1,223,051
Amortized cost	1,029,863	1,223,051
Fair value
Fixed maturities without a single maturity date (fair value)	947,778	1,248,191
Fair value	$ 947,778	$ 1,248,191
% of Total fair value
Fixed maturities without a single maturity date (% of total fair value)	8.40%	10.10%
Non-agency RMBS
Amortized cost
Fixed maturities without a single maturity date	$ 151,907	$ 185,854
Amortized cost	151,907	185,854
Fair value
Fixed maturities without a single maturity date (fair value)	133,534	186,164
Fair value	$ 133,534	$ 186,164
% of Total fair value
Fixed maturities without a single maturity date (% of total fair value)	1.20%	1.50%
ABS
Amortized cost
Fixed maturities without a single maturity date	$ 1,499,728	$ 1,628,739
Amortized cost	1,499,728	1,628,739
Fair value
Fixed maturities without a single maturity date (fair value)	1,429,527	1,622,480
Fair value	$ 1,429,527	$ 1,622,480
% of Total fair value
Fixed maturities without a single maturity date (% of total fair value)	12.60%	13.20%