v3.26.1
Interest-bearing loans and borrowings - long term - Summary of non convertible debentures (Secured) (Detail) - Secured Non Convertible Debentures
₨ / shares in Units, ₨ in Millions, $ in Millions
 12 Months Ended
Mar. 31, 2026
INR (₨)
₨ / shares
shares
Mar. 31, 2026
USD ($)
shares
Mar. 31, 2025
INR (₨)
shares
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Net of transaction cost ₨ 79,827 $ 851 ₨ 72,974
Transaction costs, discount on issue and premium on redemption 7,767 83 4,102
Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Net of transaction cost ₨ 72,060 $ 768 ₨ 68,872
Tranche One | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 1,590 1,590 1,945
Net of transaction cost ₨ 1,590 $ 17 ₨ 1,945
Interest rate % 9.75% 9.75%  
Earliest redemption date Sep. 30, 2025    
Last date of repayment Oct. 31, 2026    
Terms of repayment Half yearly    
Tranche Two | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 865 865 951
Net of transaction cost ₨ 865 $ 9 ₨ 951
Interest rate % 9.10% 9.10%  
Earliest redemption date Sep. 30, 2025    
Last date of repayment Sep. 30, 2034    
Terms of repayment Half yearly    
Tranche Three | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 3,603 3,603 3,964
Net of transaction cost ₨ 3,603 $ 38 ₨ 3,964
Interest rate % 9.10% 9.10%  
Earliest redemption date Sep. 30, 2025    
Last date of repayment Sep. 30, 2034    
Terms of repayment Half yearly    
Tranche Four | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 1,239 1,239 1,342
Net of transaction cost ₨ 1,239 $ 13 ₨ 1,342
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Five | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 5,412 5,412 5,863
Net of transaction cost ₨ 5,412 $ 58 ₨ 5,863
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Six | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 3,068 3,068 3,323
Net of transaction cost ₨ 3,068 $ 33 ₨ 3,323
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Seven | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 9,377 9,377 10,157
Net of transaction cost ₨ 9,377 $ 100 ₨ 10,157
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Eight | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 1,388 1,388 1,504
Net of transaction cost ₨ 1,388 $ 15 ₨ 1,504
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Nine | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 2,931 2,931 3,175
Net of transaction cost ₨ 2,931 $ 31 ₨ 3,175
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Ten | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 1,000,000    
Numbers of NCDs outstanding | shares 3,546 3,546 3,841
Net of transaction cost ₨ 3,546 $ 38 ₨ 3,841
Interest rate % 6.03% 6.03%  
Earliest redemption date Feb. 28, 2026    
Last date of repayment Aug. 22, 2026    
Terms of repayment Yearly    
Tranche Eleven | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares     25,000
Net of transaction cost | ₨     ₨ 2,500
Interest rate % 9.55% 9.55%  
Earliest redemption date Aug. 11, 2026    
Last date of repayment Aug. 11, 2026    
Terms of repayment Bullet    
Tranche Twelve | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares     36,732,513
Net of transaction cost | ₨     ₨ 367
Interest rate % 11.50% 11.50%  
Earliest redemption date Dec. 05, 2052    
Last date of repayment Dec. 05, 2052    
Terms of repayment Bullet    
Tranche Thirteen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares     26,661,237
Net of transaction cost | ₨     ₨ 267
Interest rate % 11.50% 11.50%  
Earliest redemption date Feb. 16, 2053    
Last date of repayment Feb. 16, 2053    
Terms of repayment Bullet    
Tranche Fourteen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares     9,594,200
Net of transaction cost | ₨     ₨ 96
Interest rate % 11.50% 11.50%  
Earliest redemption date Nov. 09, 2053    
Last date of repayment Nov. 09, 2053    
Terms of repayment Bullet    
Tranche Fifteen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares     23,598,000
Net of transaction cost | ₨     ₨ 236
Interest rate % 11.50% 11.50%  
Earliest redemption date Nov. 09, 2053    
Last date of repayment Nov. 09, 2053    
Terms of repayment Bullet    
Tranche Sixteen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 20,000 20,000 20,000
Net of transaction cost ₨ 2,000 $ 21 ₨ 2,000
Interest rate % 9.30% 9.30%  
Earliest redemption date Jun. 01, 2026    
Last date of repayment Jun. 01, 2026    
Terms of repayment Bullet    
Tranche Seventeen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 1,500 1,500 1,500
Net of transaction cost ₨ 150 $ 2 ₨ 150
Interest rate % 10.24% 10.24%  
Earliest redemption date May 25, 2026    
Last date of repayment May 25, 2026    
Terms of repayment Bullet    
Tranche Eighteen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 136,500 136,500  
Net of transaction cost ₨ 13,650 $ 145  
Interest rate % 9.90% 9.90%  
Earliest redemption date Dec. 15, 2026    
Last date of repayment Dec. 15, 2026    
Terms of repayment Bullet    
Tranche Nineteen | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares     80,000
Net of transaction cost | ₨     ₨ 8,000
Interest rate % 10.18% 10.18%  
Earliest redemption date Apr. 30, 2025    
Last date of repayment Apr. 30, 2025    
Terms of repayment Bullet    
Tranche Twenty | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 52,500 52,500 65,000
Net of transaction cost ₨ 5,250 $ 56 ₨ 6,500
Interest rate % 9.43% 9.43%  
Earliest redemption date Jan. 01, 2027    
Last date of repayment Jan. 01, 2027    
Terms of repayment Yearly    
Tranche Twenty One | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares     19,903,929
Net of transaction cost | ₨     ₨ 199
Interest rate % 11.50% 11.50%  
Earliest redemption date Jun. 28, 2054    
Last date of repayment Jun. 28, 2054    
Terms of repayment Bullet    
Tranche Twenty Two | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares     6,799,118
Net of transaction cost | ₨     ₨ 68
Interest rate % 11.50% 11.50%  
Earliest redemption date Jun. 28, 2054    
Last date of repayment Jun. 28, 2054    
Terms of repayment Bullet    
Tranche Twenty Three | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 10    
Numbers of NCDs outstanding | shares 19,626,496 19,626,496 19,626,496
Net of transaction cost ₨ 196 $ 2 ₨ 196
Interest rate % 11.50% 11.50%  
Earliest redemption date Jun. 28, 2054    
Last date of repayment Jun. 28, 2054    
Terms of repayment Bullet    
Tranche Twenty Four | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares     50,000
Net of transaction cost | ₨     ₨ 5,000
Interest rate % 10.18% 10.18%  
Earliest redemption date Aug. 22, 2025    
Last date of repayment Aug. 22, 2025    
Terms of repayment Bullet    
Tranche Twenty Five | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Non listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 60,000 60,000 0
Net of transaction cost ₨ 6,000 $ 64  
Interest rate % 10.20% 10.20%  
Earliest redemption date Dec. 31, 2026    
Last date of repayment Dec. 31, 2026    
Terms of repayment Bullet    
Tranche Twenty Six | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 48,802 48,802  
Net of transaction cost ₨ 4,880 $ 52  
Interest rate % 7.69% 7.69%  
Earliest redemption date Mar. 27, 2029    
Last date of repayment Mar. 27, 2029    
Terms of repayment Quarterly    
Tranche Twenty Seven | Gross carrying amount      
Disclosure Of Detailed Information About Secured Non Convertible Debentures [Line Items]      
Listing status Listed    
Face value per NCD | ₨ / shares ₨ 100,000    
Numbers of NCDs outstanding | shares 69,158 69,158 72,278
Net of transaction cost ₨ 6,916 $ 74 ₨ 7,228
Interest rate % 8.44% 8.44%  
Earliest redemption date Jun. 30, 2025    
Last date of repayment Aug. 31, 2029    
Terms of repayment Quarterly