REINSURANCE - Effect of Reinsurance and Retrocessional Activity on Premiums Written and Earned and on Net Claims and Claim Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Premiums Written
Direct	$ 172,696	$ 301,105
Assumed	2,617,565	2,641,859
Ceded	(526,558)	(777,747)
Net premiums written	2,263,703	2,165,217
Premiums Earned
Direct	254,019	242,761
Assumed	1,843,669	1,690,268
Ceded	(417,138)	(446,604)
Net premiums earned	1,680,550	1,486,425
Claims and Claim Expenses
Gross claims and claim expenses incurred	959,704	1,017,555
Claims and claim expenses recovered	(158,504)	(175,822)
Net claims and claim expenses incurred	$ 801,200	$ 841,733