v3.26.1
Hedging activities and derivatives - Summary Of Hedge Reserve Movement (Detail)
₨ in Millions, $ in Millions
 12 Months Ended
Mar. 31, 2026
INR (₨)
Mar. 31, 2026
USD ($)
Mar. 31, 2025
INR (₨)
Mar. 31, 2024
INR (₨)
Mar. 31, 2026
USD ($)
Disclosure of detailed information about hedges [line items]          
Beginning balance ₨ 131,112   ₨ 121,697 ₨ 118,400  
Gain / (loss) recognised on cash flow hedges 2,925 $ 31 633 (2,340)  
Income tax relating on cash flow hedges and cost of hedge reserve 464 5 (10) (626)  
Closing balance 125,860   112,602   $ 1,340
Ending balance 144,396 1,538 131,112 121,697  
Cash Flow Hedge Reserve          
Disclosure of detailed information about hedges [line items]          
Beginning balance (30) (0) 32 1,679  
Gain / (loss) recognised on cash flow hedges 18,463 197 3,015 (2,715)  
(Gain) / loss reclassified to profit or loss (under head finance costs) (15,539) (166) (2,370) 406  
(Gain)/loss reclassified to profit or loss on unwinding of derivative contract     (12) (11)  
(Gain) / loss reclassified to non financial assets or liabilities as basis adjustment (under head property, plant and equipment) (971) (10) (718) (75)  
Income tax relating on cash flow hedges and cost of hedge reserve (373) (4) (12) 594  
Closing balance 1,550   (65) (122) 17
Less: Non-controlling interest movement (67) (1) 35 154  
Ending balance 1,483 16 (30) 32  
Cost Of Hedge Reserve On Cash Flow Hedges          
Disclosure of detailed information about hedges [line items]          
Beginning balance (560) (6) (1,899) (2,297)  
Effective portion of changes in fair value (2,549) (27) (2,160) (3,346)  
Amount reclassified to profit or loss (under head "Finance costs and fair value change in derivative instruments") 1,129 12 1,421 2,435  
(Gain)/loss reclassified to profit or loss on unwinding of derivative contract 187 2 0 400  
(Gain) / loss reclassified to non financial assets or liabilities as basis adjustment (under head property, plant and equipment) 1,484 16 2,624 1,177  
Income tax relating on cash flow hedges and cost of hedge reserve (91) (1) (458) (243)  
Closing balance (400)   (472) (1,874) $ (4)
Less: Non-controlling interest movement     (88) (25)  
Ending balance (400) (4) (560) (1,899)  
Total Hedge Reserve [Member]          
Disclosure of detailed information about hedges [line items]          
Beginning balance (590) (6) (1,867) (618)  
OCI for the year 1,227 13 (93) (2,205)  
(Gain) / loss reclassified to non financial assets or liabilities as basis adjustment (under head property, plant and equipment) 513 5 1,422 827  
Attributable to non-controlling interests (67) (1) (53) 129  
Ending balance ₨ 1,083 $ 12 ₨ (590) ₨ (1,867)