v3.25.2
Loans and Allowance for Credit Losses (Loan Modifications) (Details) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Commercial | Domestic | Interest rate reduction    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 436 ¥ 3,110
Percentage of Total Class of Loans 0.00% 0.01%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Commercial | Domestic | Term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 296,078 ¥ 315,702
Percentage of Total Class of Loans 0.48% 0.55%
Loans Modified within 12 months of Subsequent Default ¥ 5,819 ¥ 5,201
Commercial | Domestic | Combination of interest rate reduction and term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 4,934 ¥ 7,038
Percentage of Total Class of Loans 0.01% 0.01%
Loans Modified within 12 months of Subsequent Default ¥ 88 ¥ 0
Commercial | Domestic | Combination of term extension and principal forgiveness    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Commercial | Domestic | All other modifications and combinations    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Commercial | Foreign | Interest rate reduction    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 1,720
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Commercial | Foreign | Term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 85,363 ¥ 83,764
Percentage of Total Class of Loans 0.18% 0.18%
Loans Modified within 12 months of Subsequent Default ¥ 912 ¥ 227
Commercial | Foreign | Combination of interest rate reduction and term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 82
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Commercial | Foreign | Combination of term extension and principal forgiveness    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Commercial | Foreign | All other modifications and combinations    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Residential | Foreign | Interest rate reduction    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Residential | Foreign | Term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 9,826 ¥ 14,842
Percentage of Total Class of Loans 0.08% 0.12%
Loans Modified within 12 months of Subsequent Default ¥ 243 ¥ 105
Residential | Foreign | Combination of interest rate reduction and term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Residential | Foreign | Combination of term extension and principal forgiveness    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Residential | Foreign | All other modifications and combinations    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Card | Foreign | Interest rate reduction    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Card | Foreign | Term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Card | Foreign | Combination of interest rate reduction and term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 24,338 ¥ 23,689
Percentage of Total Class of Loans 4.88% 4.89%
Loans Modified within 12 months of Subsequent Default ¥ 2,686 ¥ 3,038
Card | Foreign | Combination of term extension and principal forgiveness    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 234 ¥ 226
Percentage of Total Class of Loans 0.05% 0.05%
Loans Modified within 12 months of Subsequent Default ¥ 2 ¥ 3
Card | Foreign | All other modifications and combinations    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Krungsri | Foreign | Interest rate reduction    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 811 ¥ 621
Percentage of Total Class of Loans 0.01% 0.01%
Loans Modified within 12 months of Subsequent Default ¥ 326 ¥ 85
Krungsri | Foreign | Term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 196,337 ¥ 254,892
Percentage of Total Class of Loans 2.22% 2.89%
Loans Modified within 12 months of Subsequent Default ¥ 22,432 ¥ 10,030
Krungsri | Foreign | Combination of interest rate reduction and term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 13,248 ¥ 1,863
Percentage of Total Class of Loans 0.15% 0.02%
Loans Modified within 12 months of Subsequent Default ¥ 1,218 ¥ 263
Krungsri | Foreign | Combination of term extension and principal forgiveness    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 4,064 ¥ 239
Percentage of Total Class of Loans 0.05% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 31 ¥ 2,074
Krungsri | Foreign | All other modifications and combinations    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 4,475 ¥ 657
Percentage of Total Class of Loans 0.05% 0.01%
Loans Modified within 12 months of Subsequent Default ¥ 70 ¥ 62
Other | Foreign | Interest rate reduction    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 2,014 ¥ 606
Percentage of Total Class of Loans 0.10% 0.03%
Loans Modified within 12 months of Subsequent Default ¥ 68 ¥ 304
Other | Foreign | Term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 7,412 ¥ 6,464
Percentage of Total Class of Loans 0.36% 0.37%
Loans Modified within 12 months of Subsequent Default ¥ 1,343 ¥ 415
Other | Foreign | Combination of interest rate reduction and term extension    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 345
Percentage of Total Class of Loans 0.00% 0.02%
Loans Modified within 12 months of Subsequent Default ¥ 4 ¥ 0
Other | Foreign | Combination of term extension and principal forgiveness    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0
Other | Foreign | All other modifications and combinations    
Financing Receivable, Modifications [Line Items]    
Amortized Cost Basis at the Period End ¥ 0 ¥ 0
Percentage of Total Class of Loans 0.00% 0.00%
Loans Modified within 12 months of Subsequent Default ¥ 0 ¥ 0