Schedule of Amortized Cost and Estimated Fair Value of Company's Fixed Maturities Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	$ 1,331,715	$ 1,330,310
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	2,907	5,657
Fixed maturities, Gross Unrealized losses	(11,060)	(10,465)
Fixed maturities, Estimated Fair Value	1,323,562	1,325,502
U.S. Treasuries
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	675,406	640,533
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	22	216
Fixed maturities, Gross Unrealized losses	(165)	(120)
Fixed maturities, Estimated Fair Value	675,263	640,629
Obligations of States and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	14,493	14,515
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	0	0
Fixed maturities, Gross Unrealized losses	(384)	(350)
Fixed maturities, Estimated Fair Value	14,109	14,165
Mortgage Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	198,081	199,901
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	1,112	2,610
Fixed maturities, Gross Unrealized losses	(3,510)	(3,451)
Fixed maturities, Estimated Fair Value	195,683	199,060
Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	148,969	139,690
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	838	1,227
Fixed maturities, Gross Unrealized losses	(3,828)	(3,649)
Fixed maturities, Estimated Fair Value	145,979	137,268
Commercial Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	56,197	58,202
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	400	89
Fixed maturities, Gross Unrealized losses	(1,457)	(1,463)
Fixed maturities, Estimated Fair Value	55,140	56,828
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	169,967	198,970
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	343	1,090
Fixed maturities, Gross Unrealized losses	(980)	(867)
Fixed maturities, Estimated Fair Value	169,330	199,193
Foreign Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities, Amortized Cost	68,602	78,499
Fixed maturities, Allowance for Expected Credit Losses	0	0
Fixed maturities, Gross Unrealized Gains	192	425
Fixed maturities, Gross Unrealized losses	(736)	(565)
Fixed maturities, Estimated Fair Value	$ 68,058	$ 78,359

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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