Summary of Significant Accounting Policies - Effects of Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Premiums Written
Net	$ 5,380,000	$ 4,460,000	$ 3,980,000
Premiums Earned
Direct	5,196,699	4,368,342	4,022,611
Ceded	(136,698)	(109,445)	(80,950)
Assumed	15,455	15,481	10,821
Net	5,075,456	4,274,378	3,952,482
Property & Casualty
Premiums Written
Direct	5,474,292	4,531,942	4,018,057
Ceded	(138,015)	(109,644)	(81,256)
Assumed	15,489	15,353	10,743
Net	5,351,766	4,437,651	3,947,544
Premiums Earned
Direct	5,167,342	4,339,333	3,993,771
Ceded	(136,698)	(109,445)	(80,950)
Assumed	15,455	15,481	10,821
Net	$ 5,046,099	$ 4,245,369	$ 3,923,642

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