v3.26.1
Derivative Financial Instruments (Summary of Notional and Fair Value Amounts of Derivative Instruments Outstanding) (Detail) - JPY (¥)
¥ in Billions
Mar. 31, 2026
Mar. 31, 2025
Derivatives, Fair Value [Line Items]    
Notional amount [1] ¥ 3,895,722 ¥ 3,041,160
Interest rate contracts    
Derivatives, Fair Value [Line Items]    
Notional amount [1] 3,456,811 2,673,102
Foreign exchange contracts    
Derivatives, Fair Value [Line Items]    
Notional amount [1] 391,538 318,749
Equity-related contracts    
Derivatives, Fair Value [Line Items]    
Notional amount [1] 19,645 14,584
Credit-related contracts    
Derivatives, Fair Value [Line Items]    
Notional amount [1] 27,092 33,847
Other contracts    
Derivatives, Fair Value [Line Items]    
Notional amount [1] 636 878
Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 0 0
Fair value of derivative payables [2] 0 0
Designated as Hedging Instrument | Interest rate contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 0 0
Fair value of derivative payables [2] 0 0
Designated as Hedging Instrument | Foreign exchange contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 0 0
Fair value of derivative payables [2] 0 0
Designated as Hedging Instrument | Equity-related contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 0 0
Fair value of derivative payables [2] 0 0
Designated as Hedging Instrument | Credit-related contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 0 0
Fair value of derivative payables [2] 0 0
Designated as Hedging Instrument | Other contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 0 0
Fair value of derivative payables [2] 0 0
Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 23,782 15,891
Fair value of derivative payables [2] 24,205 16,267
Not Designated as Hedging Instrument | Interest rate contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 16,440 10,830
Fair value of derivative payables [2] 16,892 10,910
Not Designated as Hedging Instrument | Foreign exchange contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 6,725 4,534
Fair value of derivative payables [2] 6,566 4,813
Not Designated as Hedging Instrument | Equity-related contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 355 261
Fair value of derivative payables [2] 550 313
Not Designated as Hedging Instrument | Credit-related contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 206 245
Fair value of derivative payables [2] 134 210
Not Designated as Hedging Instrument | Other contracts    
Derivatives, Fair Value [Line Items]    
Fair value of derivative receivables [2] 57 21
Fair value of derivative payables [2] ¥ 63 ¥ 21
[1] Notional amount includes the sum of gross long and gross short third-party contracts.
[2] Derivative receivables and payables are recorded in Trading account assets and Trading account liabilities, respectively.