v3.25.2
Investments in fixed maturity securities - Narrative (Detail)
Jun. 30, 2025
Dec. 31, 2024
Summary of Investment Holdings [Line Items]    
Investment, Type [Extensible Enumeration] us-gaap:USTreasuryBillSecuritiesMember us-gaap:USTreasuryBillSecuritiesMember
AA or Higher Credit Rating [Member]    
Summary of Investment Holdings [Line Items]    
Percentage of fixed maturity investments by credit rating 93.00%  
Investment, Type [Extensible Enumeration] Debt Security, Government, Non-US [Member]