Liability for Unpaid Losses and Loss Adjustment Expenses - Change in Liability for Unpaid Losses and LAE (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at beginning of period	$ 267,760	$ 472,829
Less: Reinsurance recoverable	(123,221)	(393,365)
Net balance at beginning of period	144,539	79,464
Incurred (recovered) related to current year	130,707	113,279
Incurred (recovered) related to prior years	4,341	(185)
Total incurred	135,048	113,094
Paid related to Current year	61,778	34,549
Paid related to Prior years	87,989	60,724
Total paid	149,767	95,273
Net balance at end of period	129,820	97,285
Plus: Reinsurance recoverable	(66,158)	(269,071)
Balance at end of period	$ 195,978	$ 366,356