v3.26.1
Intangible assets (Details 1)
₨ in Millions, $ in Millions
 12 Months Ended
Mar. 31, 2026
INR (₨)
Mar. 31, 2026
USD ($)
Mar. 31, 2025
INR (₨)
Mar. 31, 2024
INR (₨)
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning ₨ 696      
Balance at ending 601 $ 6 ₨ 696  
Intangible Assets Other Than Goodwill 601   696 ₨ 641
Gross carrying amount [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning 4,062   3,646  
Acquisitions during the year 371   467  
Deletions/Adjustments during the year 693   51  
Balance at ending 3,740   4,062  
Accumulated depreciation [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning (3,366)   (3,005)  
Acquisitions during the year (466)   (406)  
Deletions/Adjustments during the year (693)   (45)  
Balance at ending (3,139)   (3,366)  
Bandwidth Capacity [Member]        
Disclosure of detailed information about intangible assets [line items]        
Intangible Assets Other Than Goodwill 72   0 1
Bandwidth Capacity [Member] | Gross carrying amount [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning 773   773  
Acquisitions during the year 83   0  
Deletions/Adjustments during the year 0   0  
Balance at ending 856   773  
Bandwidth Capacity [Member] | Accumulated depreciation [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning (773)   (772)  
Acquisitions during the year (11)   (1)  
Deletions/Adjustments during the year 0   0  
Balance at ending (784)   (773)  
Computer software [member]        
Disclosure of detailed information about intangible assets [line items]        
Intangible Assets Other Than Goodwill 507   671 612
Computer software [member] | Gross carrying amount [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning 3,211   2,795  
Acquisitions during the year 288   467  
Deletions/Adjustments during the year 673   51  
Balance at ending 2,826   3,211  
Computer software [member] | Accumulated depreciation [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning (2,540)   (2,183)  
Acquisitions during the year (452)   (402)  
Deletions/Adjustments during the year (673)   (45)  
Balance at ending (2,319)   (2,540)  
Licences and franchises [member]        
Disclosure of detailed information about intangible assets [line items]        
Intangible Assets Other Than Goodwill 22   25 ₨ 28
Licences and franchises [member] | Gross carrying amount [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning 78   78  
Acquisitions during the year 0   0  
Deletions/Adjustments during the year 20   0  
Balance at ending 58   78  
Licences and franchises [member] | Accumulated depreciation [member]        
Disclosure of detailed information about intangible assets [line items]        
Balance at beginning (53)   (50)  
Acquisitions during the year (3)   (3)  
Deletions/Adjustments during the year (20)   0  
Balance at ending ₨ (36)   ₨ (53)