v3.25.1
Investments (Securities in a gross unrealized loss position by ratings) (Details) - USD ($)
$ in Millions
Mar. 31, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value $ 25,846 $ 27,338
Gross Unrealized Losses 2,767 3,040
U.S. Government, Government agencies and Government-sponsored enterprises    
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value 2,212 2,567
Gross Unrealized Losses 322 373
AAA    
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value 1,453 1,830
Gross Unrealized Losses 265 283
AA    
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value 3,981 4,257
Gross Unrealized Losses 701 730
A    
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value 6,254 6,340
Gross Unrealized Losses 527 582
BBB    
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value 10,922 11,548
Gross Unrealized Losses 849 980
Non-investment grade    
Debt Securities, Available-for-sale [Line Items]    
Estimated Fair Value 1,024 796
Gross Unrealized Losses $ 103 $ 92