v3.26.3
Investments (Securities Held In Unrealized Loss Position And Insured By Financial Guarantor) (Detail) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Schedule Of Investments [Line Items]    
Fair value $ 820 $ 646
Financial Guarantee [Member]    
Schedule Of Investments [Line Items]    
Fair value 98  
Unrealized loss (58)  
Insurance loss reserve [1] 22  
Asset-backed [Member] | Financial Guarantee [Member]    
Schedule Of Investments [Line Items]    
Fair value 16  
Unrealized loss (3)  
Insurance loss reserve [1] 18  
Mortgage-backed [Member] | Financial Guarantee [Member]    
Schedule Of Investments [Line Items]    
Fair value 5  
Unrealized loss 0  
Insurance loss reserve [1] 4  
Corporate Obligations [Member] | Financial Guarantee [Member]    
Schedule Of Investments [Line Items]    
Fair value 77  
Unrealized loss (55)  
Insurance loss reserve [1] $ 0  
[1] Insurance loss reserve estimates are based on the proportion of par value owned to the total amount of par value insured and are discounted using a discount rate equal to the risk-free rate applicable to the currency and weighted average remaining life of the insurance contract and may differ from the fair value.