Reinsurance - Insurance Entities' Reinsurance Arrangements (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reinsurance Disclosures [Abstract]
Direct premiums written	$ 334,553	$ 289,234
Ceded premiums written	(27)	0
Net premiums written	334,526	289,234
Direct premiums earned	325,951	295,377
Ceded premiums earned	(105,122)	(85,650)
Premiums earned, net	220,829	209,727
Direct losses and loss adjustment expenses	173,243	115,742
Ceded Losses and Loss Adjustment Expenses	(38,195)	(2,648)
Net Losses and Loss Adjustment Expenses	$ 135,048	$ 113,094