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