Premiums and Reinsurance Related Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Written premiums:
Written premiums, direct	$ 3,310,893	$ 3,039,066
Written premiums, assumed	373,046	323,689
Written premiums, ceded	(550,637)	(511,464)
Total net premiums written	3,133,302	2,851,291
Earned premiums:
Earned premiums, direct	3,233,843	2,936,643
Earned premiums, assumed	339,596	337,911
Earned premiums, ceded	(561,058)	(510,207)
Net premiums earned	3,012,381	2,764,347
Ceded losses and loss expenses incurred	314,252	305,951
Ceded commissions earned	$ 139,604	$ 121,054