v3.26.1
Financial instruments (Details 4) - INR (₨)
₨ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
US Dollars [Member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges ₨ 45,777 ₨ 68,478
US Dollars [Member] | Not later than one month [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 4,770 6,535
US Dollars [Member] | Later than one month and not later than three months [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 9,996 13,069
US Dollars [Member] | Later than three months and not later than six months [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 11,949 18,616
US Dollars [Member] | Later than six months and not later than one year [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 19,062 30,258
Russian Roubles [Member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 1,874 2,557
Russian Roubles [Member] | Not later than one month [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 419 716
Russian Roubles [Member] | Later than one month and not later than three months [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 1,455 1,841
Russian Roubles [Member] | Later than three months and not later than six months [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 0 0
Russian Roubles [Member] | Later than six months and not later than one year [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 0 0
Brazilian Reals [Member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 90 (1,525)
Brazilian Reals [Member] | Not later than one month [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 90 (256)
Brazilian Reals [Member] | Later than one month and not later than three months [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 0 (513)
Brazilian Reals [Member] | Later than three months and not later than six months [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges 0 (756)
Brazilian Reals [Member] | Later than six months and not later than one year [member]    
Disclosure of detailed information about hedged items [line items]    
Forecast cash flows classified as cash flow hedges ₨ 0 ₨ 0