v3.26.1
Stock-based compensation plans - Summary of The weighted-average fair value of the units on the grant date of the restricted stock units (Detail) - Restricted share units [member] - JPY (¥)
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
July 25, 2023 [Member]      
Disclosure of terms and conditions of share-based payment arrangement [line items]      
Date of grant of share-based payment arrangement     July 25, 2023
Weighted average fair value at measurement date, other equity instruments granted     ¥ 2,587
November 27, 2023 [Member]      
Disclosure of terms and conditions of share-based payment arrangement [line items]      
Date of grant of share-based payment arrangement     November 27, 2023
Weighted average fair value at measurement date, other equity instruments granted     ¥ 2,532
July 25, 2024 [Member]      
Disclosure of terms and conditions of share-based payment arrangement [line items]      
Date of grant of share-based payment arrangement   July 25, 2024  
Weighted average fair value at measurement date, other equity instruments granted   ¥ 2,644  
November 25, 2024 [Member]      
Disclosure of terms and conditions of share-based payment arrangement [line items]      
Date of grant of share-based payment arrangement   November 25, 2024  
Weighted average fair value at measurement date, other equity instruments granted   ¥ 2,944  
July 25, 2025 [Member]      
Disclosure of terms and conditions of share-based payment arrangement [line items]      
Date of grant of share-based payment arrangement July 25, 2025    
Weighted average fair value at measurement date, other equity instruments granted ¥ 3,663    
November 25, 2025 [Member]      
Disclosure of terms and conditions of share-based payment arrangement [line items]      
Date of grant of share-based payment arrangement November 25, 2025    
Weighted average fair value at measurement date, other equity instruments granted ¥ 4,351,000,000