v3.25.2
Loss and Loss Adjustment Expense Reserves (Schedule of Losses and Loss Adjustment Expenses Reserves and Recoveries) (Detail) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Loss And Lae Reserves [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Loss and loss adjustment expense reserves [1] $ 526 $ 526
Insurance Loss Recoverable [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Insurance Loss Recoverable 185 185
Non Variable Interest Entity [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Insurance Loss Recoverable 185 185
Loss and loss adjustment expense reserves 526 526
US Public Finance Insurance [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Insurance Loss Recoverable 164 165
Loss and loss adjustment expense reserves [1] 295 299
International And Structured Finance Insurance [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Insurance Loss Recoverable 25 23
Loss and loss adjustment expense reserves [1] 237 238
International And Structured Finance Insurance [Member] | Non Variable Interest Entity [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Insurance Loss Recoverable 21 20
Loss and loss adjustment expense reserves [1] 231 227
Consolidation Elimination [Member] | International And Structured Finance Insurance [Member] | Variable Interest Entity, Primary Beneficiary [Member]    
Loss And Loss Adjustment Expense Reserves [Line Items]    
Insurance Loss Recoverable (4) (3)
Loss and loss adjustment expense reserves [1] $ (6) $ (11)
[1] Amounts are net of estimated recoveries of expected future claims.