v3.26.1
Loans and Allowance for Credit Losses (Narrative) (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Credit allowance to borrowers experiencing financial difficulty      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Other commitments ¥ 98,864 ¥ 81,151  
Nonperforming loans      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Decrease from charge-offs in the allowance for credit losses due to loan disposal activity ¥ 30,300 48,400 ¥ 15,700
Minimum | Close Watch      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Accruing loans contractually past due, in day 90 days    
Commercial      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Significant sales of loans ¥ 4,042,000 ¥ 3,778,000 ¥ 2,788,000
Commercial | Minimum      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Loans contractually past due before being placed on nonaccrual status, in month 1 month    
Commercial | Minimum | Close Watch      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Accruing loans contractually past due, in day 90 days    
Residential | Minimum      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Loans contractually past due before being placed on nonaccrual status, in month 6 months    
Card | Minimum      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Loans contractually past due before being placed on nonaccrual status, in month 3 months    
Krungsri | Minimum      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Loans contractually past due before being placed on nonaccrual status, in month 3 months    
Krungsri | Minimum | Under-Performing      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Cumulative period of loans for categorizing internal borrower ratings, commencing from the contractual due date, in day 30 days    
Krungsri | Minimum | Non-Performing      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Cumulative period of loans for categorizing internal borrower ratings, commencing from the contractual due date, in day 90 days    
MUAH | Minimum      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Loans contractually past due before being placed on nonaccrual status, in month 3 months