v3.25.2
Derivative Financial Instruments (Gains and Losses for Trading and Risk Management Derivatives (Not Designated as Hedging Instruments)) (Detail) - JPY (¥)
¥ in Billions
 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]      
Total ¥ 351 ¥ (1,363) ¥ 304
Interest rate contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total (239) (221) 272
Foreign exchange contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 438 (402) 60
Equity contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 196 (618) (13)
Commodity contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 (1) 0
Credit derivatives      
Derivative Instruments, Gain (Loss) [Line Items]      
Total (10) (27) (20)
Other      
Derivative Instruments, Gain (Loss) [Line Items]      
Total (34) (94) 5
Foreign exchange gains (losses)—net      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 447 (411) 57
Foreign exchange gains (losses)—net | Interest rate contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 0 0
Foreign exchange gains (losses)—net | Foreign exchange contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 438 (402) 60
Foreign exchange gains (losses)—net | Equity contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 0 0
Foreign exchange gains (losses)—net | Commodity contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 0 0
Foreign exchange gains (losses)—net | Credit derivatives      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 0 0
Foreign exchange gains (losses)—net | Other      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 9 (9) (3)
Trading account profits (losses)—net      
Derivative Instruments, Gain (Loss) [Line Items]      
Total (96) (952) 247
Trading account profits (losses)—net | Interest rate contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total (239) (221) 272
Trading account profits (losses)—net | Foreign exchange contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 0 0
Trading account profits (losses)—net | Equity contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 196 (618) (13)
Trading account profits (losses)—net | Commodity contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Total 0 (1) 0
Trading account profits (losses)—net | Credit derivatives      
Derivative Instruments, Gain (Loss) [Line Items]      
Total (10) (27) (20)
Trading account profits (losses)—net | Other      
Derivative Instruments, Gain (Loss) [Line Items]      
Total ¥ (43) ¥ (85) ¥ 8