v3.26.1
Credit Quality of Financial Assets and the Allowance for Credit Losses - Summary of Financing Receivables Payment Default and Modifications of Past Due (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Interest rate reduction      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified ¥ 0 ¥ 0 ¥ 25
Interest rate reduction | Consumer borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 25
Interest rate reduction | Consumer borrowers | Real estate loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     3
Interest rate reduction | Consumer borrowers | Card loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     18
Interest rate reduction | Consumer borrowers | Other      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 4
Interest rate reduction | Corporate borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Interest rate reduction | Corporate borrowers | Commercial, industrial and other companies | Overseas [Member]      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Interest rate reduction | Corporate borrowers | Other than non-recourse loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Term extension      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 8,142 0 212
Term extension | Consumer borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 212
Term extension | Consumer borrowers | Real estate loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Term extension | Consumer borrowers | Card loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Term extension | Consumer borrowers | Other      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 212
Term extension | Corporate borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 8,142 0  
Term extension | Corporate borrowers | Commercial, industrial and other companies | Overseas [Member]      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 8,142 0  
Term extension | Corporate borrowers | Other than non-recourse loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 8,142 0  
Principal forgiveness      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0 1
Principal forgiveness | Consumer borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 1
Principal forgiveness | Consumer borrowers | Real estate loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Principal forgiveness | Consumer borrowers | Card loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     1
Principal forgiveness | Consumer borrowers | Other      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 0
Principal forgiveness | Corporate borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Principal forgiveness | Corporate borrowers | Commercial, industrial and other companies | Overseas [Member]      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Principal forgiveness | Corporate borrowers | Other than non-recourse loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Combination - interest rate reduction and term extension      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 7,637 0
Combination - interest rate reduction and term extension | Consumer borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   17 0
Combination - interest rate reduction and term extension | Consumer borrowers | Real estate loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Combination - interest rate reduction and term extension | Consumer borrowers | Card loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Combination - interest rate reduction and term extension | Consumer borrowers | Other      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   17 0
Combination - interest rate reduction and term extension | Corporate borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 7,620  
Combination - interest rate reduction and term extension | Corporate borrowers | Commercial, industrial and other companies | Overseas [Member]      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 7,620  
Combination - interest rate reduction and term extension | Corporate borrowers | Other than non-recourse loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 7,620  
Combination - interest rate reduction and principal forgiveness      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0 33
Combination - interest rate reduction and principal forgiveness | Consumer borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 33
Combination - interest rate reduction and principal forgiveness | Consumer borrowers | Real estate loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Combination - interest rate reduction and principal forgiveness | Consumer borrowers | Card loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     28
Combination - interest rate reduction and principal forgiveness | Consumer borrowers | Other      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 5
Combination - interest rate reduction and principal forgiveness | Corporate borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Combination - interest rate reduction and principal forgiveness | Corporate borrowers | Commercial, industrial and other companies | Overseas [Member]      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Combination - interest rate reduction and principal forgiveness | Corporate borrowers | Other than non-recourse loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Combination - term extension and principal forgiveness      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0 9
Combination - term extension and principal forgiveness | Consumer borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 9
Combination - term extension and principal forgiveness | Consumer borrowers | Real estate loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Combination - term extension and principal forgiveness | Consumer borrowers | Card loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified     0
Combination - term extension and principal forgiveness | Consumer borrowers | Other      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified   0 ¥ 9
Combination - term extension and principal forgiveness | Corporate borrowers      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Combination - term extension and principal forgiveness | Corporate borrowers | Commercial, industrial and other companies | Overseas [Member]      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified 0 0  
Combination - term extension and principal forgiveness | Corporate borrowers | Other than non-recourse loans      
Financing Receivable, Modified, Subsequent Default [Line Items]      
Financing Receivable, Modified ¥ 0 ¥ 0