v3.26.1
Deferred tax assets (DTA) (net) / deferred tax liabilities (DTL) (net) - Summary of Deferred Tax Liabilities (Net) (Detail)
₨ in Millions, $ in Millions
Mar. 31, 2026
INR (₨)
Mar. 31, 2026
USD ($)
Mar. 31, 2025
INR (₨)
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities ₨ 27,127 $ 289 ₨ 24,481
Deferred Tax Assets [Abstract]      
Deferred tax assets 10,319 110 7,073
Net Deferred Tax Liabilities      
Deferred Tax Assets [Abstract]      
Deferred tax liabilities (net) 27,127 289 24,481
Deferred Tax Assets | Net Deferred Tax Liabilities      
Deferred Tax Assets [Abstract]      
Deferred tax assets 44,203 471 45,562
Deferred Tax Assets | Net Deferred Tax Liabilities | Mark to market of derivative instruments      
Deferred Tax Assets [Abstract]      
Deferred tax assets     14
Deferred Tax Assets | Net Deferred Tax Liabilities | Unamortized ancillary borrowing cost      
Deferred Tax Assets [Abstract]      
Deferred tax assets 2 0 9
Deferred Tax Assets | Net Deferred Tax Liabilities | Provision for decommissioning costs      
Deferred Tax Assets [Abstract]      
Deferred tax assets 1,635 17 1,685
Deferred Tax Assets | Net Deferred Tax Liabilities | Expected credit losses      
Deferred Tax Assets [Abstract]      
Deferred tax assets 304 3 399
Deferred Tax Assets | Net Deferred Tax Liabilities | Losses and unabsorbed depreciation available for offsetting against future taxable income      
Deferred Tax Assets [Abstract]      
Deferred tax assets 37,244 397 39,487
Deferred Tax Assets | Net Deferred Tax Liabilities | Unused tax credit (Minimum alternate tax)      
Deferred Tax Assets [Abstract]      
Deferred tax assets 3,395 36 2,722
Deferred Tax Assets | Net Deferred Tax Liabilities | Lease Liabilities      
Deferred Tax Assets [Abstract]      
Deferred tax assets 1,025 11 737
Deferred Tax Assets | Net Deferred Tax Liabilities | Government grant (viability gap funding)      
Deferred Tax Assets [Abstract]      
Deferred tax assets 334 4 355
Deferred Tax Assets | Net Deferred Tax Liabilities | Others      
Deferred Tax Assets [Abstract]      
Deferred tax assets 264 3 154
Deferred Tax Liabilities | Net Deferred Tax Liabilities      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities 71,330 760 70,043
Deferred Tax Liabilities | Net Deferred Tax Liabilities | Compound financial instruments      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities 430 5 195
Deferred Tax Liabilities | Net Deferred Tax Liabilities | Mark to market of derivative instruments      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities 637 7 797
Deferred Tax Liabilities | Net Deferred Tax Liabilities | Difference in written down value of PPE as per books of account and tax laws      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities 69,084 736 68,256
Deferred Tax Liabilities | Net Deferred Tax Liabilities | Unamortized ancillary borrowing cost      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities 141 1 168
Deferred Tax Liabilities | Net Deferred Tax Liabilities | Right of use asset      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities 880 9 561
Deferred Tax Liabilities | Net Deferred Tax Liabilities | Others      
Deferred Tax Liabilities [Abstract]      
Deferred tax liabilities ₨ 158 $ 2 ₨ 66