REINSURANCE - Credit Quality Indicator (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	$ 46,845,921	$ 39,343,524
Credit enhancements	42,639,725	34,025,326
Net reinsurance credit exposure	4,580,128	5,318,426
Credit loss allowance	24,800	21,000
A++
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	44,895	38,857
Credit enhancements	0	0
Net reinsurance credit exposure	44,895	38,857
A+
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	1,779,822	1,801,954
Credit enhancements	0	0
Net reinsurance credit exposure	1,779,822	1,801,954
A
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	2,223,845	2,212,800
Credit enhancements	0	0
Net reinsurance credit exposure	2,223,845	2,212,800
A-
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	4,259,094	4,430,484
Credit enhancements	3,728,593	3,814,976
Net reinsurance credit exposure	530,501	615,508
B++
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	1,065	589
Credit enhancements	0	0
Net reinsurance credit exposure	1,065	589
B+
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	0	0
Credit enhancements	0	0
Net reinsurance credit exposure	0	0
B
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	0	0
Credit enhancements	0	0
Net reinsurance credit exposure	0	0
B-
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	0	0
Credit enhancements	0	0
Net reinsurance credit exposure	0	0
C++/C+
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	(228)	(228)
Credit enhancements	0	0
Net reinsurance credit exposure	0	0
Not rated or private rating
Ceded Credit Risk [Line Items]
Reinsurance recoverable and funds withheld receivable at interest	38,537,428	30,859,068
Credit enhancements	38,911,132	30,210,350
Net reinsurance credit exposure	0	648,718
Net reinsurance credit exposure associated with cessions to co-investment vehicles	$ 38,500,000	$ 30,800,000