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General - Effects of Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Premiums Written
Direct	$ 1,465,700	$ 1,237,200	$ 4,154,100	$ 3,395,200
Premiums Earned
Ceded	42,400	30,900	104,900	78,100
Net	1,320,652	1,090,311	3,723,355	3,129,483
Property & Casualty
Premiums Written
Direct	1,458,934	1,230,024	4,133,920	3,374,477
Ceded	(42,938)	(30,889)	(106,121)	(78,463)
Assumed	137	195	15,381	15,293
Net	1,416,133	1,199,330	4,043,180	3,311,307
Premiums Earned
Direct	1,351,870	1,110,013	3,794,663	3,174,296
Ceded	(42,444)	(30,917)	(104,894)	(78,114)
Assumed	3,856	3,883	11,578	11,630
Net	$ 1,313,282	$ 1,082,979	$ 3,701,347	$ 3,107,812

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