v3.26.1
Short-Term Borrowings and Long-Term Debt (Interest Rates and Maturities of Senior Borrowings and Bonds, and Subordinated Borrowings and Bonds) (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Debt Instrument [Line Items]    
Borrowings and bonds ¥ 20,445,265 ¥ 14,611,098
Senior borrowings and bonds    
Debt Instrument [Line Items]    
Borrowings and bonds 16,673,563 11,072,660
Senior borrowings and bonds | Fixed Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Borrowings and bonds 4,676,495 1,519,315
Senior borrowings and bonds | Fixed Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Borrowings and bonds 5,124,262 4,382,480
Senior borrowings and bonds | Fixed Rate | Denominated in other currencies    
Debt Instrument [Line Items]    
Borrowings and bonds 2,993,771 2,347,671
Senior borrowings and bonds | Floating Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Borrowings and bonds 765,345 591,004
Senior borrowings and bonds | Floating Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Borrowings and bonds 3,095,371 2,175,327
Senior borrowings and bonds | Floating Rate | Denominated in other currencies    
Debt Instrument [Line Items]    
Borrowings and bonds 18,320 56,863
Subordinated borrowings and bonds    
Debt Instrument [Line Items]    
Borrowings and bonds 3,771,702 3,538,438
Subordinated borrowings and bonds | Fixed Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Borrowings and bonds 3,611,772 3,276,760
Subordinated borrowings and bonds | Fixed Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Borrowings and bonds ¥ 159,930 ¥ 261,678
Minimum | Senior borrowings and bonds | Fixed Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Interest rates [1] 0.00%  
Maturities, Start [2] 2026-04  
Minimum | Senior borrowings and bonds | Fixed Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Interest rates [1] 0.00%  
Maturities, Start [2] 2026-04  
Minimum | Senior borrowings and bonds | Fixed Rate | Denominated in other currencies    
Debt Instrument [Line Items]    
Interest rates [1] 0.00%  
Maturities, Start [2] 2026-04  
Minimum | Senior borrowings and bonds | Floating Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Interest rates [1] 0.00%  
Maturities, Start [2] 2026-04  
Minimum | Senior borrowings and bonds | Floating Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Interest rates [1] 0.00%  
Maturities, Start [2] 2026-04  
Minimum | Senior borrowings and bonds | Floating Rate | Denominated in other currencies    
Debt Instrument [Line Items]    
Interest rates [1] 0.00%  
Maturities, Start [2] 2027-09  
Minimum | Subordinated borrowings and bonds | Fixed Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Interest rates [1] 0.41%  
Maturities, Start [2] 2026-06  
Minimum | Subordinated borrowings and bonds | Fixed Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Interest rates [1] 2.56%  
Maturities, Start [2] 2031-09  
Maximum | Senior borrowings and bonds | Fixed Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Interest rates [1] 5.15%  
Maturities, End [2] 2056-03  
Maximum | Senior borrowings and bonds | Fixed Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Interest rates [1] 5.95%  
Maturities, End [2] 2048-03  
Maximum | Senior borrowings and bonds | Fixed Rate | Denominated in other currencies    
Debt Instrument [Line Items]    
Interest rates [1] 6.03%  
Maturities, End [2] 2041-05  
Maximum | Senior borrowings and bonds | Floating Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Interest rates [1] 25.00%  
Maturities, End [2] 2081-09  
Maximum | Senior borrowings and bonds | Floating Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Interest rates [1] 169.50%  
Maturities, End [2] 2067-11  
Maximum | Senior borrowings and bonds | Floating Rate | Denominated in other currencies    
Debt Instrument [Line Items]    
Interest rates [1] 10.00%  
Maturities, End [2] 2041-09  
Maximum | Subordinated borrowings and bonds | Fixed Rate | Denominated in Japanese yen    
Debt Instrument [Line Items]    
Interest rates [1] 4.26%  
Maximum | Subordinated borrowings and bonds | Fixed Rate | Denominated in U.S. dollars    
Debt Instrument [Line Items]    
Interest rates [1] 2.56%  
Maturities, End [2] 2031-09  
[1] The interest rates disclosed reflect the range of contractual rates in effect at March 31, 2026.
[2] Maturity information disclosed is the range of maturities at March 31, 2026.