v3.26.3
Investments - Summary of Amortized Cost, Allowance for Credit Loss, Gross Unrealized Gains and Losses, and Estimated Fair Value of Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Cost or Amortized Cost $ 1,295,000 $ 595,383
Fixed-maturity securities, Allowance for Credit Loss 0 0
Fixed-maturity securities, Gross Unrealized Gains 19 3,322
Fixed-maturity securities, Gross Unrealized Losses (53,575) (1,376)
Fixed-maturity securities, available-for-sale, at fair value [1] 1,241,444 597,329
U.S. Treasury and U.S. Government Agencies [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Allowance for Credit Loss 0 0
Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Allowance for Credit Loss 0 0
Commercial Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Allowance for Credit Loss 0 0
Fixed-Maturity Securities [Member] | U.S. Treasury and U.S. Government Agencies [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Cost or Amortized Cost 1,028,239 332,284
Fixed-maturity securities, Gross Unrealized Gains 0 1,785
Fixed-maturity securities, Gross Unrealized Losses (46,835) (717)
Fixed-maturity securities, available-for-sale, at fair value 981,404 333,352
Fixed-Maturity Securities [Member] | Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Cost or Amortized Cost 241,905 241,843
Fixed-maturity securities, Gross Unrealized Gains 1 1,463
Fixed-maturity securities, Gross Unrealized Losses (6,063) (384)
Fixed-maturity securities, available-for-sale, at fair value 235,843 242,922
Fixed-Maturity Securities [Member] | Commercial Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Fixed-maturity securities, Cost or Amortized Cost 24,856 21,256
Fixed-maturity securities, Gross Unrealized Gains 18 74
Fixed-maturity securities, Gross Unrealized Losses (677) (275)
Fixed-maturity securities, available-for-sale, at fair value $ 24,197 $ 21,055
[1] See Note 12 for details of balances associated with consolidated variable interest entities.