Schedule of Amortized Cost and Estimated Fair Value of Company's Fixed Maturities Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	$ 1,341,934	$ 1,394,639
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	3,989	2,205
Fixed maturities, Gross Unrealized losses	(9,579)	(14,936)
Fixed maturities, Estimated Fair Value	1,336,344	1,381,908
U.S. Treasuries
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	572,608	875,273
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	38	757
Fixed maturities, Gross Unrealized losses	(265)	(784)
Fixed maturities, Estimated Fair Value	572,381	875,246
Obligations of States and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	15,923	17,125
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	0	0
Fixed maturities, Gross Unrealized losses	(489)	(790)
Fixed maturities, Estimated Fair Value	15,434	16,335
Mortgage Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	216,275	61,905
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	1,216	299
Fixed maturities, Gross Unrealized losses	(2,500)	(3,284)
Fixed maturities, Estimated Fair Value	214,991	58,920
Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	158,153	137,445
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	1,141	864
Fixed maturities, Gross Unrealized losses	(2,166)	(2,882)
Fixed maturities, Estimated Fair Value	157,128	135,427
Commercial Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	66,382	68,041
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	395	15
Fixed maturities, Gross Unrealized losses	(1,573)	(2,488)
Fixed maturities, Estimated Fair Value	65,204	65,568
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	223,657	158,798
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	898	189
Fixed maturities, Gross Unrealized losses	(1,547)	(2,891)
Fixed maturities, Estimated Fair Value	223,008	156,096
Foreign Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	88,936	76,052
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	301	81
Fixed maturities, Gross Unrealized losses	(1,039)	(1,817)
Fixed maturities, Estimated Fair Value	$ 88,198	$ 74,316

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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