INVESTMENTS - Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Fair value
12 months or greater	$ 1,806,373	$ 2,253,146
Less than 12 months	3,443,339	4,880,934
Total	5,249,712	7,134,080
Unrealized losses
12 months or greater	(133,042)	(185,909)
Less than 12 months	(74,722)	(125,426)
Total	(207,764)	(311,335)
U.S. government and agency
Fair value
12 months or greater	205,838	262,368
Less than 12 months	375,531	1,026,139
Total	581,369	1,288,507
Unrealized losses
12 months or greater	(9,688)	(17,515)
Less than 12 months	(2,383)	(15,621)
Total	(12,071)	(33,136)
Non-U.S. government
Fair value
12 months or greater	72,109	98,846
Less than 12 months	225,680	457,889
Total	297,789	556,735
Unrealized losses
12 months or greater	(5,984)	(9,179)
Less than 12 months	(6,591)	(16,781)
Total	(12,575)	(25,960)
Corporate debt
Fair value
12 months or greater	738,285	934,975
Less than 12 months	1,614,646	2,032,254
Total	2,352,931	2,967,229
Unrealized losses
12 months or greater	(57,868)	(78,979)
Less than 12 months	(39,791)	(47,245)
Total	(97,659)	(126,224)
Agency RMBS
Fair value
12 months or greater	255,353	280,550
Less than 12 months	573,326	749,040
Total	828,679	1,029,590
Unrealized losses
12 months or greater	(27,160)	(35,333)
Less than 12 months	(15,577)	(26,657)
Total	(42,737)	(61,990)
CMBS
Fair value
12 months or greater	328,574	410,213
Less than 12 months	231,417	260,411
Total	559,991	670,624
Unrealized losses
12 months or greater	(17,768)	(22,334)
Less than 12 months	(8,475)	(11,836)
Total	(26,243)	(34,170)
Non-agency RMBS
Fair value
12 months or greater	48,450	69,418
Less than 12 months	52,389	8,302
Total	100,839	77,720
Unrealized losses
12 months or greater	(5,905)	(9,900)
Less than 12 months	(111)	(82)
Total	(6,016)	(9,982)
ABS
Fair value
12 months or greater	122,630	147,281
Less than 12 months	361,590	295,897
Total	484,221	443,178
Unrealized losses
12 months or greater	(6,532)	(8,471)
Less than 12 months	(1,589)	(4,806)
Total	(8,121)	(13,277)
Municipals
Fair value
12 months or greater	35,134	49,495
Less than 12 months	8,760	51,002
Total	43,893	100,497
Unrealized losses
12 months or greater	(2,137)	(4,198)
Less than 12 months	(205)	(2,398)
Total	$ (2,342)	$ (6,596)