v3.26.1
Investments - Summary of Securities with Gross Unrealized Loss Positions Aggregated by Investment Category (Detail) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less than Twelve Months $ (6,485) $ (1,117)
Estimated Fair Value, Less than Twelve Months 712,237 253,325
Gross Unrealized Losses, Twelve Months or Longer (339) (259)
Estimated Fair Value, Twelve Months or Longer 4,325 4,105
Gross Unrealized Losses, Total (6,824) (1,376)
Estimated Fair Value, Total 716,562 257,430
Fixed-Maturity Securities [Member] | U.S. Treasury and U.S. Government Agencies [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less than Twelve Months (5,289) (553)
Estimated Fair Value, Less than Twelve Months 529,963 208,273
Gross Unrealized Losses, Twelve Months or Longer (166) (164)
Estimated Fair Value, Twelve Months or Longer 2,915 2,918
Gross Unrealized Losses, Total (5,455) (717)
Estimated Fair Value, Total 532,878 211,191
Fixed-Maturity Securities [Member] | Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less than Twelve Months (1,001) (289)
Estimated Fair Value, Less than Twelve Months 165,245 28,303
Gross Unrealized Losses, Twelve Months or Longer (173) (95)
Estimated Fair Value, Twelve Months or Longer 1,410 1,187
Gross Unrealized Losses, Total (1,174) (384)
Estimated Fair Value, Total 166,655 29,490
Fixed-Maturity Securities [Member] | Commercial Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross Unrealized Losses, Less than Twelve Months (195) (275)
Estimated Fair Value, Less than Twelve Months 17,029 16,749
Gross Unrealized Losses, Twelve Months or Longer 0 0
Estimated Fair Value, Twelve Months or Longer 0 0
Gross Unrealized Losses, Total (195) (275)
Estimated Fair Value, Total $ 17,029 $ 16,749