v3.26.1
Employee Benefits - Summary of Change in Plan Assets (Detail) - INR (₨)
₨ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Disclosure of net defined benefit liability (asset) [line items]      
Fair value of plan assets at the beginning of the year ₨ 22,231 ₨ 20,022  
Fair value of plan assets 29,837 22,231 ₨ 20,022
Return on plan assets excluding interest income 879 1,646 1,828
Fair value of plan assets at the end of the year 29,837 22,231 20,022
Present value of unfunded obligation (2,744) (1,957)  
Change in the effect of asset ceiling (678) (545)  
Recognized liability (3,422) (2,502)  
Effect of asset ceiling at the beginning of the year 545 442  
Interest expense on effect of asset ceiling 25 17  
Changes in the effect of limiting the surplus to the asset ceiling 6 74  
Translation adjustment 102 12  
Effect of asset ceiling at the end of the year 678 545 442
Plan assets [member]      
Disclosure of net defined benefit liability (asset) [line items]      
Addition through Business combination 211 0  
Expected return on plan assets 1,263 1,230  
Employer contributions 5,417 141  
Benefits paid (188) (313)  
Contributions from plan participants and due to transfer 87 558  
Return on plan assets excluding interest income (384) 416  
Translation adjustment 1,200 177  
Present value of defined benefit obligation [member]      
Disclosure of net defined benefit liability (asset) [line items]      
Defined benefit obligation (asset) 32,581 24,188 21,516
Benefits paid 2,631 2,627  
Contributions from plan participants and due to transfer (87) (558)  
Value at the end of the year ₨ 32,581 ₨ 24,188 ₨ 21,516