v3.26.1
Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments Held by Successor Ambac, by Contractual Maturity (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost $ 231,537 $ 269,848
Debt Securities, Available-for-Sale 229,387 268,737
Amortized Cost, Due in one year or less 117,446 180,013
Amortized Cost, Due after one year through five years 47,546 32,409
Amortized Cost, Due after five years through ten years 55,344 47,801
Amortized Cost, Due after ten years 550 979
Amortized Cost, Total 220,886 261,202
Estimated Fair Value, Due in one year or less 117,313 179,824
Estimated Fair Value, Due after one year through five years 45,845 31,588
Estimated Fair Value, Due after five years through ten years 55,042 47,619
Estimated Fair Value, Due after ten years 553 998
Estimated Fair Value due, Total 218,753 260,029
Fixed Income Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 139,242 123,414
Debt Securities, Available-for-Sale 137,092 122,295
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 2,643 1,604
Debt Securities, Available-for-Sale 2,627 1,597
Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 5,002 3,307
Debt Securities, Available-for-Sale 4,985 3,341
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 1,626 1,963
Debt Securities, Available-for-Sale 1,630 1,975
Fixed Income Securities [Member] | Asset-backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 1,380 1,772
Debt Securities, Available-for-Sale $ 1,392 $ 1,795