v3.26.1
Other Assets - Schedule of Goodwill (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Goodwill [Roll Forward]          
Goodwill beginning balance     $ 190 $ 551 $ 551
Goodwill impairment $ 0 $ 0 0 (305) (305)
Transfer to assets of operations held-for-sale         (56)
Goodwill ending balance 190   190   190
Operating Segments | Automotive Finance operations          
Goodwill [Roll Forward]          
Goodwill beginning balance     20 20 20
Goodwill impairment     0 0 0
Transfer to assets of operations held-for-sale         0
Goodwill ending balance 20   20   20
Operating Segments | Insurance operations          
Goodwill [Roll Forward]          
Goodwill beginning balance     27 27 27
Goodwill impairment     0 0 0
Transfer to assets of operations held-for-sale         0
Goodwill ending balance 27   27   27
Corporate and Other          
Goodwill [Roll Forward]          
Goodwill beginning balance     143 504 504
Goodwill impairment     0 $ (305) (305)
Transfer to assets of operations held-for-sale         (56)
Goodwill ending balance 143   143   143
Corporate and Other | Ally Invest          
Goodwill [Roll Forward]          
Goodwill beginning balance     143    
Goodwill ending balance $ 143   $ 143   $ 143