v3.26.1
Stock-based compensation plans - Summary of Unexercised Stock Acquisition Rights (Detail)
 12 Months Ended
Mar. 31, 2026
shares
¥ / shares
Mar. 31, 2025
shares
Mar. 31, 2024
shares
Mar. 31, 2026
shares
$ / shares
Mar. 31, 2023
shares
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Exercise term exercisable up to 10 years from the date of grant. exercisable up to 10 years from the date of grant. exercisable up to 10 years from the date of grant.    
Number of share options outstanding in share-based payment arrangement 65,014,900 81,169,300 97,809,500 65,014,900 98,457,500
Series 28th date of options Granted on November20, 2014 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 20, 2014        
Exercise term November 20, 2015 to November 19, 2024        
Exercise price | ¥ / shares ¥ 483        
Number of share options outstanding in share-based payment arrangement     417,500    
Series 29th date of options Granted on November20, 2014 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 20, 2014        
Exercise term November 20, 2015 to November 19, 2024        
Exercise price | $ / shares       $ 4.14  
Number of share options outstanding in share-based payment arrangement     613,500    
Series 30th date of options Granted on November19, 2015 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 19, 2015        
Exercise term November 19, 2016 to November 18, 2025        
Exercise price | ¥ / shares ¥ 681        
Number of share options outstanding in share-based payment arrangement   230,500 445,000    
Series 31st date of options Granted on November19, 2015 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 19, 2015        
Exercise term November 19, 2016 to November 18, 2025        
Exercise price | $ / shares       $ 4.68  
Number of share options outstanding in share-based payment arrangement   337,000 656,500    
Series 32nd date of options Granted on November22, 2016 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 22, 2016        
Exercise term November 22, 2017 to November 21, 2026        
Exercise price | ¥ / shares ¥ 673        
Number of share options outstanding in share-based payment arrangement 404,500 755,500 1,157,000 404,500  
Series 33rd date of options Granted on November22, 2016 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 22, 2016        
Exercise term November 22, 2017 to November 21, 2026        
Exercise price | $ / shares       $ 5.39  
Number of share options outstanding in share-based payment arrangement 476,500 983,000 1,430,500 476,500  
Series 34th date of options Granted on November21, 2017 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 21, 2017        
Exercise term November 21, 2018 to November 20, 2027        
Exercise price | ¥ / shares ¥ 1,047        
Number of share options outstanding in share-based payment arrangement 629,000 944,500 1,401,000 629,000  
Series 35th date of options Granted on November21, 2017 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 21, 2017        
Exercise term November 21, 2018 to November 20, 2027        
Exercise price | $ / shares       $ 8.32  
Number of share options outstanding in share-based payment arrangement 1,005,000 1,486,500 2,528,500 1,005,000  
Series 36th date of options Granted on February28, 2018 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant February 28, 2018        
Exercise term February 28, 2019 to February 27, 2028        
Exercise price | ¥ / shares ¥ 1,089        
Number of share options outstanding in share-based payment arrangement 3,000 4,500 7,500 3,000  
Series 38th date of options Granted on November20, 2018 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 20, 2018        
Exercise term November 20, 2019 to November 19, 2028        
Exercise price | ¥ / shares ¥ 1,288        
Number of share options outstanding in share-based payment arrangement 1,681,000 2,308,500 2,983,500 1,681,000  
Series 39th date of options Granted on November20, 2018 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 20, 2018        
Exercise term November 20, 2019 to November 19, 2028        
Exercise price | $ / shares       $ 10.42  
Number of share options outstanding in share-based payment arrangement 1,326,500 1,926,500 3,271,500 1,326,500  
Series 40th date of options Granted on November20, 2019 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 20, 2019        
Exercise term November 20, 2020 to November 19, 2029        
Exercise price | ¥ / shares ¥ 1,341        
Number of share options outstanding in share-based payment arrangement 1,706,000 2,799,000 4,373,000 1,706,000  
Series 41st date of options Granted on November20, 2019 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 20, 2019        
Exercise term November 20, 2020 to November 19, 2029        
Exercise price | $ / shares       $ 11.37  
Number of share options outstanding in share-based payment arrangement 2,356,000 2,736,000 4,582,000 2,356,000  
Series 43rd date of options Granted on November18, 2020 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 18, 2020        
Exercise term November 18, 2021 to November 17, 2030        
Exercise price | ¥ / shares ¥ 1,848        
Number of share options outstanding in share-based payment arrangement 4,247,000 6,386,000 8,270,000 4,247,000  
Series 44th date of options Granted on November18, 2020 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 18, 2020        
Exercise term November 18, 2021 to November 17, 2030        
Exercise price | $ / shares       $ 16.67  
Number of share options outstanding in share-based payment arrangement 4,117,500 5,641,000 8,573,000 4,117,500  
Series 45th date of options Granted on November 18 2021 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 18, 2021        
Exercise term November 18, 2022 to November 17, 2031        
Exercise price | ¥ / shares ¥ 2,870        
Number of share options outstanding in share-based payment arrangement 7,535,500 10,635,000 11,656,000 7,535,500  
Series 46th date of options Granted on November 18 2021 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 18, 2021        
Exercise term November 18, 2022 to November 17, 2031        
Exercise price | $ / shares       $ 24.15  
Number of share options outstanding in share-based payment arrangement 7,206,000 10,119,500 10,689,000 7,206,000  
Series 47th date of options Granted on November 16 2022 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 16, 2022        
Exercise term November 16, 2023 to November 15, 2032        
Exercise price | ¥ / shares ¥ 2,278        
Number of share options outstanding in share-based payment arrangement 8,823,000 10,686,500 12,006,000 8,823,000  
Series 48th date of options Granted on November 16 2022 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 16, 2022        
Exercise term November 16, 2023 to November 15, 2032        
Exercise price | $ / shares       $ 14.75  
Number of share options outstanding in share-based payment arrangement 6,079,500 7,836,500 10,620,000 6,079,500  
Series 49th date of options Granted on November 27 2023 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 27, 2023        
Exercise term November 27, 2024 to November 26, 2033        
Exercise price | ¥ / shares ¥ 2,589        
Number of share options outstanding in share-based payment arrangement 5,950,500 6,392,000 6,471,000 5,950,500  
Series 50th date of options Granted on November 27 2023 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 27, 2023        
Exercise term November 27, 2024 to November 26, 2033        
Exercise price | $ / shares       $ 16.27  
Number of share options outstanding in share-based payment arrangement 4,292,500 4,658,500 5,657,500 4,292,500  
Series 51th Date Of Options Granted On November 25 2024 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 25, 2024        
Exercise term November 25, 2025 to November 24, 2034        
Exercise price | ¥ / shares ¥ 2,948        
Number of share options outstanding in share-based payment arrangement 2,844,800 2,867,000   2,844,800  
Series 52th Date Of Options Granted On November 25 2024 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 25, 2024        
Exercise term November 25, 2025 to November 24, 2034        
Exercise price | $ / shares       $ 18.1  
Number of share options outstanding in share-based payment arrangement 1,362,100 1,435,800   1,362,100  
Series 53th Date Of Options Granted On November 25 2025 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 25, 2025        
Exercise term November 25, 2026 to November 24, 2035        
Exercise price | ¥ / shares ¥ 4,512        
Number of share options outstanding in share-based payment arrangement 2,030,700     2,030,700  
Series 54th Date Of Options Granted On November 25 2025 [Member]          
Disclosure of terms and conditions of share-based payment arrangement [line items]          
Date of grant November 25, 2025        
Exercise term November 25, 2026 to November 24, 2035        
Exercise price | $ / shares       $ 28.88  
Number of share options outstanding in share-based payment arrangement 938,300     938,300