Schedule VI - Supplementary Information Concerning Property-Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Deferred policy acquisition costs	$ 951,728	$ 861,609	$ 763,486
Reserves for losses and loss expenses	20,368,030	18,739,652	17,011,223
Unearned premiums	6,375,112	5,922,326	5,297,654
Net premiums earned	11,548,485	10,400,687	9,561,429
Net investment income	1,333,161	1,052,835	779,185
Losses and loss expenses incurred:
Current year	7,083,999	6,311,780	5,774,713
Prior years	14,350	29,681	54,511
Loss reserve discount accretion	33,246	30,681	32,526
Amortization of deferred policy acquisition costs		1,038,975	1,038,903
Paid losses and loss expenses	5,484,430	4,981,610	4,347,910
Net premiums written	$ 11,972,096	$ 10,954,467	$ 10,004,070