Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Number of Consolidated FG VIEs (Details) - Variable Interest Entity, Primary Beneficiary	12 Months Ended
	Dec. 31, 2024 Entity entity	Dec. 31, 2023 Entity entity	Dec. 31, 2022 Entity entity
Financial Guaranty Variable Interest Entities | Structured finance
Schedule of Consolidated FG VIEs Rollforward [Roll Forward]
Beginning of year	24	25	25
Consolidated	0	0	2
Deconsolidated	(1)	(1)	(2)
December 31	23	24	25
Consolidated investment vehicles
Schedule of Consolidated FG VIEs Rollforward [Roll Forward]
Consolidated | entity	0	0	4
Deconsolidated | entity	(1)	(19)	(2)