INVESTMENTS - AFS in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	$ 13,074,946	$ 30,113,886
Less than 12 months, Unrealized losses	(511,585)	(4,017,293)
12 months or more, Fair value	47,396,528	27,191,183
12 months or more, Unrealized losses	(10,086,297)	(7,588,946)
Total, Fair value	60,471,474	57,305,069
Total, Unrealized losses	(10,597,882)	(11,606,239)
U.S. government and agencies
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	177,322	122,272
Less than 12 months, Unrealized losses	(2,918)	(52,639)
12 months or more, Fair value	198,376	108,498
12 months or more, Unrealized losses	(66,767)	(19,855)
Total, Fair value	375,698	230,770
Total, Unrealized losses	(69,685)	(72,494)
U.S. state, municipal and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	321,202	2,321,404
Less than 12 months, Unrealized losses	(13,832)	(605,698)
12 months or more, Fair value	3,766,538	1,780,984
12 months or more, Unrealized losses	(1,053,025)	(628,176)
Total, Fair value	4,087,740	4,102,388
Total, Unrealized losses	(1,066,857)	(1,233,874)
Corporate
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	8,821,425	14,792,384
Less than 12 months, Unrealized losses	(339,357)	(2,114,695)
12 months or more, Fair value	25,974,990	17,943,907
12 months or more, Unrealized losses	(7,058,500)	(5,869,646)
Total, Fair value	34,796,415	32,736,291
Total, Unrealized losses	(7,397,857)	(7,984,341)
Residential mortgage-backed securities, or “RMBS”
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	1,633,807	3,998,737
Less than 12 months, Unrealized losses	(49,552)	(442,543)
12 months or more, Fair value	4,845,271	2,068,529
12 months or more, Unrealized losses	(646,828)	(391,669)
Total, Fair value	6,479,078	6,067,266
Total, Unrealized losses	(696,380)	(834,212)
Collateralized bond obligations, or “CBOs”
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	0	1,351,552
Less than 12 months, Unrealized losses	0	(103,499)
12 months or more, Fair value	2,781,731	1,482,099
12 months or more, Unrealized losses	(213,268)	(114,274)
Total, Fair value	2,781,731	2,833,651
Total, Unrealized losses	(213,268)	(217,773)
Commercial mortgage-backed securities, or “CMBS”
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	545,960	4,054,053
Less than 12 months, Unrealized losses	(59,584)	(445,168)
12 months or more, Fair value	6,045,832	2,338,517
12 months or more, Unrealized losses	(741,599)	(389,567)
Total, Fair value	6,591,792	6,392,570
Total, Unrealized losses	(801,183)	(834,735)
CLOs
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	688,364	1,862,608
Less than 12 months, Unrealized losses	(4,229)	(139,766)
12 months or more, Fair value	2,258,563	636,014
12 months or more, Unrealized losses	(140,091)	(60,394)
Total, Fair value	2,946,927	2,498,622
Total, Unrealized losses	(144,320)	(200,160)
Asset-backed securities, or “ABSs”
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair value	886,866	1,610,876
Less than 12 months, Unrealized losses	(42,113)	(113,285)
12 months or more, Fair value	1,525,227	832,635
12 months or more, Unrealized losses	(166,219)	(115,365)
Total, Fair value	2,412,093	2,443,511
Total, Unrealized losses	$ (208,332)	$ (228,650)