Schedule VI-Supplementary Information Concerning Property-Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Claims and claim adjustment expenses incurred related to:
Current accident year	$ 582,065	$ 543,937	$ 488,700
Prior accident years	(125,463)	(101,053)	(75,284)
Amortization of deferred acquisition costs	317,468	286,438	288,697
Consolidated Property-Casualty Insurance Operations
Supplemental Information For Property Casualty Insurance Underwriters [Line Items]
Deferred policy acquisition costs	103,553	88,425	85,044
Claims and claim adjustment expense reserves	2,043,555	1,750,049	1,574,352
Unearned premiums, gross	680,444	586,386	540,213
Net premiums earned	980,903	865,747	839,111
Net investment income	68,862	67,893	68,870
Claims and claim adjustment expenses incurred related to:
Current accident year	582,065	543,937	488,700
Prior accident years	(125,463)	(101,053)	(75,284)
Amortization of deferred acquisition costs	317,468	286,438	288,697
Paid claims and claims adjustment expenses	327,453	325,054	319,930
Net premiums written	$ 1,057,533	$ 892,088	$ 860,337