Investments - Additional Information (Detail)	3 Months Ended
Mar. 31, 2025 USD ($) ParntershipInvestments Entity	Dec. 31, 2024 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Investments in a single issuer as a percentage of shareholders' equity	2.00%	1.70%
Number of limited partnership investments \| ParntershipInvestments	3
Fixed maturity securities with market value	$ 0	$ 0
Investments in insurance enhanced bonds	$ 1,700,000
Insurance enhanced bonds as a percentage of total cash and invested assets	0.10%
Investments in collateralized mortgage obligations, commercial mortgage-backed securities and taxable municipal bonds	$ 1,700,000
Equity securities, at fair value	12,408,000	12,284,000
Future Funding Commitments	14,214,000	14,214,000
Limited partnership investments with carrying value of fair value	$ 23,900,000	29,400,000
Variable Interest Entity, Not Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Number of VIE's \| Entity	2
Ownership interest exceeds respective investments	3.00%
One of the Company's variable interest VIE's, invests in distressed securities and assets
Schedule Of Available For Sale Securities [Line Items]
Significant variable interest in carrying value of the non-consolidated VIE	$ 2,400,000	2,600,000
Future Funding Commitments	14,200,000	14,200,000
Variable interest entities, maximum exposure to loss	16,600,000	16,800,000
Second VIE that invests in REIT qualifying assets
Schedule Of Available For Sale Securities [Line Items]
Significant variable interest in carrying value of the non-consolidated VIE	8,300,000	8,900,000
Variable interest entities, maximum exposure to loss	8,300,000	8,900,000
Assured Guaranty Corporation
Schedule Of Available For Sale Securities [Line Items]
Investments in collateralized mortgage obligations, commercial mortgage-backed securities and taxable municipal bonds	800,000
Ambac Financial Group
Schedule Of Available For Sale Securities [Line Items]
Investments in collateralized mortgage obligations, commercial mortgage-backed securities and taxable municipal bonds	900,000
Other Assets
Schedule Of Available For Sale Securities [Line Items]
Accrued interest receivable related to fixed maturities	5,000,000	3,500,000
Preferred Stock
Schedule Of Available For Sale Securities [Line Items]
Equity securities, at fair value	12,400,000	$ 12,300,000
U.S. Treasuries
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	422,000
Obligations of States and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	615,000
Mortgage Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	2,586,000
Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	$ 2,346,000
Weighted average credit enhancement	37.10%
Commercial Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	$ 1,786,000
Weighted average credit enhancement	43.80%
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	$ 2,151,000
Foreign Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Gross unrealized losses	$ 1,411,000

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