v3.26.3
Finance Receivable Sale Agreements (Details)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
agreement_type
Sep. 30, 2025
USD ($)
Jul. 27, 2026
USD ($)
Jul. 26, 2026
USD ($)
Dec. 31, 2025
USD ($)
purchaser
agreement
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Number of agreement types | agreement_type     2        
Consumer Loan | MPSA              
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Principal balances of finance receivables through securitization transactions, sold $ 2,000 $ 1,200 $ 2,000 $ 1,200      
Principal balances of finance receivables sold     5,700 3,200      
Receivable purchase agreement, remaining unused capacity 6,000   6,000        
Consumer Loan | MPSA | Ally Parties              
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Transfer of financial assets accounted for as sales, new total eligible amount to be sold 8,000   8,000   $ 8,000 $ 6,000  
Consumer Loan | Loan Purchase Agreement              
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Transfer of financial assets accounted for as sales, new total eligible amount to be sold 12,500   12,500       $ 12,000
Number of agreements | agreement             3
Number of purchasers | purchaser             3
Increase (decrease) in transfer of financial assets accounted for as sales, new total eligible amount to be sold 500            
Consumer Loan | Fixed Pool Loan Sale              
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Principal balances of finance receivables sold 1,600 1,100 4,500 3,100      
Unused capacity under the definitive loan purchase agreements 8,300   8,300        
Consumer Loan | Master Purchase and Sale Agreement and Master Transfer Agreements              
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Gain on loan sales 381 331 1,100 878      
Securitization Transaction              
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]              
Principal balances of finance receivables through securitization transactions, sold $ 1,550 $ 1,000 1,550 1,000      
Principal balances of finance receivables sold     $ 3,700 $ 2,600