Loans and Allowance for Credit Losses (Loan Modifications) (Details) - JPY (¥)
¥ in Millions |
12 Months Ended |
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
| Commercial | Domestic | Interest rate reduction |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 4
|
¥ 436
|
¥ 3,110
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.01%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 4
|
¥ 0
|
¥ 0
|
| Commercial | Domestic | Term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 311,314
|
¥ 296,078
|
¥ 315,702
|
| Percentage of Total Class of Loans |
0.48%
|
0.48%
|
0.55%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 11,150
|
¥ 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 |
¥ 702
|
¥ 4,934
|
¥ 7,038
|
| Percentage of Total Class of Loans |
0.00%
|
0.01%
|
0.01%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 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
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Commercial | Domestic | All other modifications and combinations |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Commercial | Foreign | Interest rate reduction |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 360
|
¥ 0
|
¥ 1,720
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Commercial | Foreign | Term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 72,434
|
¥ 85,363
|
¥ 83,764
|
| Percentage of Total Class of Loans |
0.13%
|
0.18%
|
0.18%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 18,380
|
¥ 912
|
¥ 227
|
| Commercial | Foreign | Combination of interest rate reduction and term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 6,280
|
¥ 0
|
¥ 82
|
| Percentage of Total Class of Loans |
0.01%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 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
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Commercial | Foreign | All other modifications and combinations |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Residential | Foreign | Interest rate reduction |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Residential | Foreign | Term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 7,797
|
¥ 9,826
|
¥ 14,842
|
| Percentage of Total Class of Loans |
0.06%
|
0.08%
|
0.12%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 89
|
¥ 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
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 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
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Residential | Foreign | All other modifications and combinations |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Card | Foreign | Interest rate reduction |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Card | Foreign | Term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Card | Foreign | Combination of interest rate reduction and term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 27,118
|
¥ 24,338
|
¥ 23,689
|
| Percentage of Total Class of Loans |
4.86%
|
4.88%
|
4.89%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 3,992
|
¥ 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 |
¥ 423
|
¥ 234
|
¥ 226
|
| Percentage of Total Class of Loans |
0.08%
|
0.05%
|
0.05%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 119
|
¥ 2
|
¥ 3
|
| Card | Foreign | All other modifications and combinations |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Krungsri | Foreign | Interest rate reduction |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 11
|
¥ 811
|
¥ 621
|
| Percentage of Total Class of Loans |
0.00%
|
0.01%
|
0.01%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 255
|
¥ 326
|
¥ 85
|
| Krungsri | Foreign | Term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 134,785
|
¥ 196,337
|
¥ 254,892
|
| Percentage of Total Class of Loans |
1.37%
|
2.22%
|
2.89%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 21,519
|
¥ 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 |
¥ 89,458
|
¥ 13,248
|
¥ 1,863
|
| Percentage of Total Class of Loans |
0.91%
|
0.15%
|
0.02%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 3,700
|
¥ 1,218
|
¥ 263
|
| Krungsri | Foreign | Combination of term extension and principal forgiveness |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 344
|
¥ 4,064
|
¥ 239
|
| Percentage of Total Class of Loans |
0.00%
|
0.05%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 4,543
|
¥ 31
|
¥ 2,074
|
| Krungsri | Foreign | All other modifications and combinations |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 1,590
|
¥ 4,475
|
¥ 657
|
| Percentage of Total Class of Loans |
0.02%
|
0.05%
|
0.01%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 37
|
¥ 70
|
¥ 62
|
| Other | Foreign | Interest rate reduction |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 1,720
|
¥ 2,014
|
¥ 606
|
| Percentage of Total Class of Loans |
0.08%
|
0.10%
|
0.03%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 840
|
¥ 68
|
¥ 304
|
| Other | Foreign | Term extension |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 5,670
|
¥ 7,412
|
¥ 6,464
|
| Percentage of Total Class of Loans |
0.26%
|
0.36%
|
0.37%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 526
|
¥ 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 |
¥ 1
|
¥ 0
|
¥ 345
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.02%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 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
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|
| Other | Foreign | All other modifications and combinations |
|
|
|
| Financing Receivable, Modifications [Line Items] |
|
|
|
| Amortized Cost Basis at the Period End |
¥ 0
|
¥ 0
|
¥ 0
|
| Percentage of Total Class of Loans |
0.00%
|
0.00%
|
0.00%
|
| Loans Modified within 12 months of Subsequent Default |
¥ 0
|
¥ 0
|
¥ 0
|