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
Jun. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost $ 219,306 $ 269,848
Debt Securities, Available-for-Sale 216,654 268,737
Amortized Cost, Due in one year or less 97,346 180,013
Amortized Cost, Due after one year through five years 57,023 32,409
Amortized Cost, Due after five years through ten years 54,868 47,801
Amortized Cost, Due after ten years 0 979
Amortized Cost, Total 209,237 261,202
Estimated Fair Value, Due in one year or less 97,257 179,824
Estimated Fair Value, Due after one year through five years 54,884 31,588
Estimated Fair Value, Due after five years through ten years 54,483 47,619
Estimated Fair Value, Due after ten years 0 998
Estimated Fair Value due, Total 206,624 260,029
Residential Mortgage-Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 2,452 1,604
Debt Securities, Available-for-Sale 2,428 1,597
Commercial Mortgage Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 4,869 3,307
Debt Securities, Available-for-Sale 4,848 3,341
Collateralized Debt Obligations [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 1,368 1,963
Debt Securities, Available-for-Sale 1,368 1,975
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 $ 1,386 $ 1,795