v3.25.2
Investments (Narrative) (Detail)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2025
USD ($)
Security
Jun. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Security
Schedule Of Investments [Line Items]      
Fair value of securities on deposit with various regulatory authorities $ 11   $ 11
Number of securities in unrealized loss position for a continuous 12 month period | Security 246   366
Rate that a security's fair value is below book value 5.00%   5.00%
Increase decrease in other net realized (gains) losses $ (7) $ 9  
Asset Pledged as Collateral [Member]      
Schedule Of Investments [Line Items]      
Fair value of securities pledged as collateral $ 214   $ 213
Securities In Unrealized Loss Position [Member]      
Schedule Of Investments [Line Items]      
Weighted average contractual maturity period in years for securities in an unrealized loss position 14 years   15 years
Fair Value Below Book Value Greater Than Five Percent [Member]      
Schedule Of Investments [Line Items]      
Number of securities in unrealized loss position for a continuous 12 month period | Security 206   318