v3.26.1
Derivative Financial Instruments (Summary of Gains and Losses on Derivatives not Designated or Qualifying as Hedges) (Parenthetical) (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recorded in income ¥ 713,441 ¥ (518,972) ¥ (560,806)
Credit-related contracts      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recorded in income [1] 22,718 (6,531) 3,053
Credit-related contracts | Loans related to credit derivatives      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) recorded in income ¥ (809) ¥ (964) ¥ (952)
[1] Amounts include the net gains (losses) of ¥(952) million, ¥(964) million and ¥(809) million on the credit derivatives economically managing the credit risk of loans during the fiscal years ended March 31, 2024, 2025 and 2026, respectively.