v3.26.3
Loans and Allowance for Loan Losses - Schedule of Current, Accruing Past Due, and Non-Accrual Loans on an Amortized Cost Basis by Loan Portfolio Class (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Sep. 30, 2025
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis $ 198 $ 41
Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 98 7
Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 2 0
Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0 0
Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 98 34
Total commercial and industrial    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 142  
Total commercial and industrial | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 84  
Total commercial and industrial | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 2  
Total commercial and industrial | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial and industrial | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 56  
Total commercial and industrial | Commercial, financial and agricultural    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 142 7
Total commercial and industrial | Commercial, financial and agricultural | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 84 7
Total commercial and industrial | Commercial, financial and agricultural | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 2 0
Total commercial and industrial | Commercial, financial and agricultural | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0 0
Total commercial and industrial | Commercial, financial and agricultural | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 56 0
Total commercial and industrial | Owner-occupied    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial and industrial | Owner-occupied | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial and industrial | Owner-occupied | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial and industrial | Owner-occupied | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial and industrial | Owner-occupied | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial real estate    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 40  
Total commercial real estate | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 9  
Total commercial real estate | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial real estate | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total commercial real estate | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 31  
Total commercial real estate | Investment properties    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 40 34
Total commercial real estate | Investment properties | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 9 0
Total commercial real estate | Investment properties | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0 0
Total commercial real estate | Investment properties | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0 0
Total commercial real estate | Investment properties | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 31 $ 34
Total consumer    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 16  
Total consumer | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 5  
Total consumer | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total consumer | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total consumer | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 11  
Total consumer | Consumer mortgages    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 14  
Total consumer | Consumer mortgages | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 3  
Total consumer | Consumer mortgages | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total consumer | Consumer mortgages | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total consumer | Consumer mortgages | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 11  
Total consumer | Other consumer loans    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 2  
Total consumer | Other consumer loans | Current    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 2  
Total consumer | Other consumer loans | Accruing 30-89 Days Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total consumer | Other consumer loans | Accruing 90 Days or Greater Past Due    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis 0  
Total consumer | Other consumer loans | Non-accrual    
Financing Receivable, Modified [Line Items]    
Amortized cost basis of loans, aging analysis $ 0