v3.26.1
Derivative instruments and hedging activities - Schedule of derivatives designated as hedging instruments and hedged items (Detail) - JPY (¥)
¥ in Billions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Hedged Items [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) on fair value hedges recognized ¥ (17) ¥ (85) ¥ 39
Hedged Items [Member] | Long-term borrowings [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) on fair value hedges recognized (17) (85) 39
Derivatives designated as hedging instruments [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) on fair value hedges recognized 17 85 (39)
Derivatives designated as hedging instruments [Member] | Interest rate contracts [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gains (losses) on fair value hedges recognized ¥ 17 ¥ 85 ¥ (39)