v3.26.1
Share based payment - Schedule of Movement of Options Outstanding under the share based payment schemes (Detail) - shares
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
2021 Incentive Award Plan      
Share Based Payment Arrangements [Line Items]      
Outstanding at the beginning of the year 57,000,000 51,000,000 36,000,000
Granted during the year 5,000,000 7,000,000 16,000,000
Lapsed during the year   1,000,000 1,000,000
Exercised/ lapsed during the year 5,000,000    
Outstanding at the end of the year 57,000,000 57,000,000 51,000,000
Exercisable at the end of the year 48,000,000 40,000,000  
2025 Employee Stock Option Plan      
Share Based Payment Arrangements [Line Items]      
Outstanding at the beginning of the year 0    
Granted during the year 6,000,000 0  
Lapsed during the year 0    
Outstanding at the end of the year 6,000,000 0  
2025 Employee Share Purchase Plan      
Share Based Payment Arrangements [Line Items]      
Granted during the year 9,000,000    
Lapsed during the year 1,000,000    
Outstanding at the end of the year 8,000,000    
Global Incentive Plan 2024      
Share Based Payment Arrangements [Line Items]      
Granted during the year 0    
Outstanding at the end of the year 0    
Exercisable at the end of the year 0    
Holding Company Stock Option Plans      
Share Based Payment Arrangements [Line Items]      
Outstanding at the beginning of the year 11,000,000 11,000,000 11,000,000
Exercised/ lapsed during the year 1,000,000 0 0
Outstanding at the end of the year 10,000,000 11,000,000 11,000,000
Exercisable at the end of the year 10,000,000 11,000,000