RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 22, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 25, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Other investments, at fair value	$ 954,571		$ 954,571		$ 954,571			$ 996,751
Acquisition costs			263,389	$ 240,511	747,027	$ 746,443
Net losses and loss expenses			783,940	941,911	2,240,840	2,444,196
Loss associated with the retroactive component of the agreement			(2,762)	(4,735)	(13,118)	(17,632)
Reinsurance recoverable on unpaid losses	6,031,527		6,031,527	5,244,263	6,031,527	5,244,263		5,831,172	$ 5,017,611
Reinsurance recoverable on paid losses and loss expenses	594,375		594,375		594,375			539,676
Insurance and reinsurance balances payable	1,900,188		1,900,188		1,900,188			$ 1,522,764
Net premiums earned			1,322,564	$ 1,284,866	3,818,508	$ 3,820,163
Eagle Point Credit Management, LLC | Director
Related Party Transaction [Line Items]
Other investments, at fair value	6,000		6,000		6,000
Aspida Holdings, Ltd | Director
Related Party Transaction [Line Items]
Other investments, at fair value	$ 5,000		5,000		5,000
Monarch Point Re | Loan With Monarch Point Re
Related Party Transaction [Line Items]
Stated interest rate (in percent)	5.70%
Monarch Point Re | Director
Related Party Transaction [Line Items]
Other investments, at fair value	$ 11,000		11,000		11,000
Monarch Point Re | Related Party
Related Party Transaction [Line Items]
Reinsurance premiums					244,000
Acquisition costs		$ 33,000
Net losses and loss expenses		7,000
Reinsurance recoverable on unpaid losses	76,000		76,000		76,000
Reinsurance recoverable on paid losses and loss expenses	4,000		4,000		4,000
Insurance and reinsurance balances payable	195,000		195,000		195,000
Net premiums earned		$ 119,000
Monarch Point Re | Related Party | Loan With Monarch Point Re
Related Party Transaction [Line Items]
Advanced amount	$ 127,000		$ 127,000		127,000		$ 156,000
Non-cash repayment of advance					$ 29,000