v3.26.1
Share-based Payments - Schedule of Stock Options and Awards (Details)
 12 Months Ended
Mar. 31, 2026
shares
¥ / shares
Mar. 31, 2025
shares
¥ / shares
Mar. 31, 2024
shares
¥ / shares
Mar. 31, 2023
shares
¥ / shares
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Granted | shares   0 0  
Exercised | ¥ / shares ¥ 1,305      
Outstanding at the end of the year (1) | ¥ / shares ¥ 1,300      
1st Stock Options        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Outstanding at the beginning of the year | shares 31,802,000 31,802,000 31,802,000  
Exercised | shares (31,802,000)      
Outstanding at the end of the year (1) | shares   31,802,000 31,802,000 31,802,000
Exercisable at the end of the year | shares   31,802,000 31,802,000  
Outstanding at the beginning of the year | ¥ / shares ¥ 500 ¥ 500 ¥ 500  
Exercised | ¥ / shares ¥ 500      
Outstanding at the end of the year (1) | ¥ / shares   500 500 ¥ 500
Exercisable at the end of the year | ¥ / shares   ¥ 500 ¥ 500  
2nd to 46th Trust-type Stock Options        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Outstanding at the beginning of the year | shares 4,011,000 4,299,000 4,516,000  
Granted | shares       4,589,000
Exercised | shares (82,000)      
Forfeited | shares (122,000) (288,000) (217,000)  
Outstanding at the end of the year (1) | shares 3,807,000 4,011,000 4,299,000 4,516,000
Exercisable at the end of the year | shares 633,000      
Outstanding at the beginning of the year | ¥ / shares ¥ 1,300 ¥ 1,300 ¥ 1,300  
Exercised | ¥ / shares 1,300      
Forfeited | ¥ / shares (1,300) (1,300) (1,300)  
Outstanding at the end of the year (1) | ¥ / shares 1,300 ¥ 1,300 ¥ 1,300 ¥ 1,300
Exercisable at the end of the year | ¥ / shares ¥ 1,300      
47th Stock Option        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Granted | shares 7,625,000      
Forfeited | shares (255,000)      
Outstanding at the end of the year (1) | shares 7,370,000      
Granted | ¥ / shares ¥ 1,300      
Forfeited | ¥ / shares (1,300)      
Outstanding at the end of the year (1) | ¥ / shares ¥ 1,300      
48th Stock Options        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Granted | shares 535,000      
Outstanding at the end of the year (1) | shares 535,000      
Granted | ¥ / shares ¥ 1,300      
Outstanding at the end of the year (1) | ¥ / shares ¥ 1,300      
49th Stock Options        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Granted | shares 569,000      
Outstanding at the end of the year (1) | shares 569,000      
Granted | ¥ / shares ¥ 1      
Outstanding at the end of the year (1) | ¥ / shares ¥ 1      
Phantom stock awards        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Outstanding at the beginning of the year | shares 79,000 79,000 79,000  
Granted | shares 155,000      
Outstanding at the end of the year (1) | shares 234,000 79,000 79,000 79,000
Exercisable at the end of the year | shares 10,000      
Outstanding at the beginning of the year | ¥ / shares ¥ 1,300 ¥ 1,300 ¥ 1,300  
Granted | ¥ / shares 1,327      
Outstanding at the end of the year (1) | ¥ / shares 1,318 ¥ 1,300 ¥ 1,300 ¥ 1,300
Exercisable at the end of the year | ¥ / shares ¥ 1,300