Schedule VI - Supplementary Information Concerning Property-Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Deferred policy acquisition costs	$ 763,486	$ 676,145	$ 556,168
Reserves for losses and loss expenses	17,011,223	15,390,888	13,784,430
Unearned premiums	5,297,654	4,847,160	4,073,191
Net premiums earned	9,561,429	8,106,031	6,930,843
Net investment income	779,185	671,618	583,821
Losses and loss expenses incurred:
Current year	5,774,713	4,921,191	4,432,937
Prior years	54,511	863	627
Loss reserve discount accretion	32,526	31,906	35,142
Amortization of deferred policy acquisition costs		961,628	904,955
Paid losses and loss expenses	4,347,910	3,665,694	3,598,649
Net premiums written	$ 10,004,070	$ 8,862,867	$ 7,262,437