v3.26.3
Credit Quality of Financial Assets and the Allowance for Credit Losses - Summary of Past Due Financial Assets Modified to Debtors (Detail) - JPY (¥)
¥ in Millions
 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified ¥ 6,326 ¥ 16,495
30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 5 0
90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 59 46
Consumer borrowers | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 57 45
Consumer borrowers | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 5 0
Consumer borrowers | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 6
Consumer borrowers | Real estate loans | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified   0
Consumer borrowers | Real estate loans | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified   0
Consumer borrowers | Real estate loans | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified   6
Consumer borrowers | Other | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 57 45
Consumer borrowers | Other | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 5 0
Consumer borrowers | Other | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 6,188 16,348
Corporate borrowers | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 20 40
Corporate borrowers | Non-recourse Loans | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 1,848  
Corporate borrowers | Non-recourse Loans | Current | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 1,848  
Corporate borrowers | Non-recourse Loans | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0  
Corporate borrowers | Non-recourse Loans | 30-89 days past-due | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0  
Corporate borrowers | Non-recourse Loans | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0  
Corporate borrowers | Non-recourse Loans | 90 days or more past-due | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0  
Corporate borrowers | Other than non-recourse loans | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 4,340 16,348
Corporate borrowers | Other than non-recourse loans | Current | Real estate companies | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 362 262
Corporate borrowers | Other than non-recourse loans | Current | Commercial, industrial and other companies | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 68 540
Corporate borrowers | Other than non-recourse loans | Current | Commercial, industrial and other companies | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 3,910 15,546
Corporate borrowers | Other than non-recourse loans | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | Other than non-recourse loans | 30-89 days past-due | Real estate companies | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | Other than non-recourse loans | 30-89 days past-due | Commercial, industrial and other companies | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | Other than non-recourse loans | 30-89 days past-due | Commercial, industrial and other companies | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | Other than non-recourse loans | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 20 40
Corporate borrowers | Other than non-recourse loans | 90 days or more past-due | Real estate companies | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 27
Corporate borrowers | Other than non-recourse loans | 90 days or more past-due | Commercial, industrial and other companies | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Corporate borrowers | Other than non-recourse loans | 90 days or more past-due | Commercial, industrial and other companies | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 20 13
Net investment in leases | Current    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 81 102
Net investment in leases | Current | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 81 102
Net investment in leases | Current | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0  
Net investment in leases | 30-89 days past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Net investment in leases | 30-89 days past-due | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 0
Net investment in leases | 30-89 days past-due | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0  
Net investment in leases | 90 days or more past-due    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 39 0
Net investment in leases | 90 days or more past-due | Japan    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified 0 ¥ 0
Net investment in leases | 90 days or more past-due | Overseas    
Financing Receivable, Modified, Subsequent Default [Line Items]    
Financing Receivable, Modified ¥ 39