Schedule IV. Supplemental Schedule of Reinsurance Premiums (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Gross Amounts	$ 1,105,164	$ 799,717	$ 536,595
Ceded to Other Companies	1,850,807	1,863,350	1,662,815
Assumed	7,079,632	6,257,814	5,078,682
Net premiums earned (Note 6)	$ 6,333,989	$ 5,194,181	$ 3,952,462
Percentage of Amount Assumed to Net	112.00%	120.00%	128.00%