v3.26.1
Derivative instruments and hedging activities - Schedule of gains (losses) from derivatives and non-derivatives designated as net investment hedges (Detail) - Hedging instruments [Member] - JPY (¥)
¥ in Billions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) from derivatives designated as net investment hedges ¥ (10) ¥ (2) ¥ 3
Foreign exchange contracts [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) from derivatives designated as net investment hedges ¥ (10) ¥ (2) ¥ 3