v3.26.1
Credit Quality of Financial Assets and the Allowance for Credit Losses - Summary of Past Due Financial Assets Modified to Debtors (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified ¥ 13,169 ¥ 24,963 ¥ 10,522
30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 2,142 91
90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 29 62 291
Consumer borrowers | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   173 35
Consumer borrowers | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   1 91
Consumer borrowers | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   17 7
Consumer borrowers | Real estate loans | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 105   1
Consumer borrowers | Real estate loans | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0   0
Consumer borrowers | Real estate loans | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 5   0
Consumer borrowers | Other | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 173 34
Consumer borrowers | Other | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 1 91
Consumer borrowers | Other | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 5 17 7
Corporate borrowers | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 105 23,857 6,140
Corporate borrowers | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 2,141 0
Corporate borrowers | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 45 284
Corporate borrowers | Non-recourse Loans | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 12,973 0 1,277
Corporate borrowers | Non-recourse Loans | Current | The Americas      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 12,973 0 1,277
Corporate borrowers | Non-recourse Loans | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 2,141 0
Corporate borrowers | Non-recourse Loans | 30-89 days past-due | The Americas      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 2,141 0
Corporate borrowers | Non-recourse Loans | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 12 0 0
Corporate borrowers | Non-recourse Loans | 90 days or more past-due | The Americas      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 12 0 0
Corporate borrowers | Other than non-recourse loans | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 443 23,857 4,863
Corporate borrowers | Other than non-recourse loans | Current | Real estate companies | Japan      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 404 1,243 37
Corporate borrowers | Other than non-recourse loans | Current | Real estate companies | Overseas      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 12,126 1,701  
Corporate borrowers | Other than non-recourse loans | Current | Commercial, industrial and other companies | Japan      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 91 623 481
Corporate borrowers | Other than non-recourse loans | Current | Commercial, industrial and other companies | Overseas      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 91 20,290 4,345
Corporate borrowers | Other than non-recourse loans | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 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 0
Corporate borrowers | Other than non-recourse loans | 30-89 days past-due | Real estate companies | Overseas      
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 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 0
Corporate borrowers | Other than non-recourse loans | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 45 284
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 29 32
Corporate borrowers | Other than non-recourse loans | 90 days or more past-due | Real estate companies | Overseas      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 12 0  
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 12 0 230
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 0 16 22
Loans to Equity Method Investees | Current      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 933 4,347
Loans to Equity Method Investees | 30-89 days past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0 0
Loans to Equity Method Investees | 90 days or more past-due      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified ¥ 12 ¥ 0 ¥ 0