v3.25.2
Business Developments And Risks And Uncertainties (Narrative) (Detail)
$ in Millions
6 Months Ended
Jul. 01, 2025
USD ($)
Jan. 01, 2025
USD ($)
Jun. 30, 2025
USD ($)
Segments
Business Acquisition [Line Items]      
Number of operating segments | Segments     3
MBIA Mexico [Member]      
Business Acquisition [Line Items]      
Capital returned by subsidiary     $ 12
Puerto Rico Electric Power Authority [Member]      
Business Acquisition [Line Items]      
Outstanding insured bonds     $ 657
National Public Finance Guarantee Corporation [Member] | Puerto Rico Electric Power Authority [Member]      
Business Acquisition [Line Items]      
Claims payments   $ 13  
Subsequent Event [Member] | National Public Finance Guarantee Corporation [Member] | Puerto Rico Electric Power Authority [Member]      
Business Acquisition [Line Items]      
Claims payments $ 92