Schedule VI - Supplemental Information Concerning Consolidated Property and Casualty Insurance Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Reserves for Unpaid Losses and LAE	$ 510,117				$ 1,038,790				$ 510,117	$ 1,038,790	$ 346,216	$ 322,465
Incurred Loss and LAE Current Year									882,064	913,419	724,755
Incurred Loss and LAE Prior Years									110,573	24,980	54,450
Paid Losses and LAE									906,064	928,645	751,792
Net investment income	13,714	$ 12,755	$ 11,282	$ 10,698	10,448	$ 6,074	$ 5,221	$ 4,042	48,449	25,785	12,535
Deferred Policy Acquisition Cost (“DPAC”)	109,985				103,654				109,985	103,654	108,822	$ 110,614
Amortization of DPAC, Net									(210,955)	(217,235)	(224,121)
Net Premiums Written									1,344,813	1,173,278	1,084,827
Net Premiums Earned	335,398	$ 331,040	$ 303,274	$ 282,224	291,870	$ 290,631	$ 277,061	$ 269,064	1,251,936	1,128,626	1,035,463
Unearned premiums	$ 990,559				$ 943,854				$ 990,559	$ 943,854	$ 857,769