v3.25.2
Due to Trust Account, Short-term Borrowings and Long-term Debt (Narrative) (Detail)
€ in Millions, ¥ in Millions, $ in Millions
12 Months Ended
Mar. 31, 2025
JPY (¥)
Mar. 31, 2025
USD ($)
Mar. 31, 2025
EUR (€)
Mar. 31, 2024
JPY (¥)
Debt Instrument [Line Items]        
Unused lines of credit for financing ¥ 3,439,902     ¥ 3,943,240
Minimum TLAC ratio, required by end of the period over risk weighted assets 18.00%      
Minimum TLAC ratio, required by end of the period over leverage ratio denominator 6.75%      
Basel III        
Debt Instrument [Line Items]        
Floor of Common Equity Tier 1 ratio, which leads the Group's discretion over unsecured perpetual subordinated Additional Tier 1 notes 5.125%      
Unsecured Perpetual Subordinated Additional Tier 1 Notes | Yen | Basel III        
Debt Instrument [Line Items]        
Aggregated principal amount of long term debt issued ¥ 358,000      
Bonds for TLAC | Euro        
Debt Instrument [Line Items]        
Aggregated principal amount of long term debt issued 162,080   € 1,000  
Bonds for TLAC | Dollars        
Debt Instrument [Line Items]        
Aggregated principal amount of long term debt issued 710,220 $ 4,750    
Subordinated Tier 2 Notes | Yen | Basel III        
Debt Instrument [Line Items]        
Aggregated principal amount of long term debt issued ¥ 363,000