Reinsurance - Impact of the Reinsurance Contracts on Premiums Written and Earned (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024		Jun. 30, 2023		Jun. 30, 2024		Jun. 30, 2023
Premiums Written:
Direct	$ 284,289		$ 179,983		$ 496,184		$ 387,406
Assumed	22,613		0		65,704		(7,569)
Gross written	306,902		179,983		561,888		379,837
Ceded	(76,713)		(66,390)		(144,819)		(136,899)
Net premiums written	230,189		113,593		417,069		242,938
Premiums Earned:
Direct	201,791		181,946		391,466		354,851
Assumed	61,770		0		128,739		7,163
Gross earned	263,561	[1]	181,946	[2]	520,205	[3]	362,014	[4]
Ceded	(76,713)		(66,390)		(144,819)		(136,899)
Net premiums earned	$ 186,848		$ 115,556		$ 375,386		$ 225,115

[1] Gross premiums earned under HCPCI Insurance Operations consist of $143,702 from HCPCI and $6,655 from a reinsurance company.

[2] Gross premiums earned under HCPCI Insurance Operations consist of $96,875 from HCPCI and $4,915 from a reinsurance company.

[3] Gross premiums earned under HCPCI Insurance Operations consist of $292,973 from HCPCI and $12,766 from a reinsurance company.

[4] Gross premiums earned under HCPCI Insurance Operations consist of $189,331 from HCPCI and $9,450 from a reinsurance company.