v3.26.1
Loans and Allowance for Credit Losses (Aging Analysis) (Details) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Current      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) ¥ 605,255 ¥ 579,550 ¥ 672,988
1-3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 33,278 39,562 31,906
Greater Than 3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 21,478 30,458 10,966
Commercial | Current | Domestic      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 310,091 300,859 324,772
Commercial | Current | Foreign      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 79,074 84,672 85,566
Commercial | 1-3 months Past Due | Domestic      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 213 442 740
Commercial | 1-3 months Past Due | Foreign      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 0 690 0
Commercial | Greater Than 3 months Past Due | Domestic      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 1,716 148 338
Commercial | Greater Than 3 months Past Due | Foreign      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 0 0 0
Residential | Current      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 7,352 8,930 13,770
Residential | 1-3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 379 742 918
Residential | Greater Than 3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 66 154 154
Card | Current      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 19,908 19,316 17,888
Card | 1-3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 5,905 3,562 3,961
Card | Greater Than 3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 1,728 1,694 2,066
Krungsri | Current      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 183,106 159,909 225,319
Krungsri | 1-3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 25,665 31,610 24,839
Krungsri | Greater Than 3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 17,418 27,416 8,114
Other | Current      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 5,724 5,864 5,673
Other | 1-3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) 1,116 2,516 1,448
Other | Greater Than 3 months Past Due      
Financing Receivable, Modifications [Line Items]      
Payment Status (Amortized Cost Basis at the Period End) ¥ 550 ¥ 1,046 ¥ 294