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Investments - Additional Information (Detail)
₨ in Millions, $ in Millions
12 Months Ended
Mar. 31, 2019
INR (₨)
Mar. 31, 2018
INR (₨)
Mar. 31, 2017
Mar. 31, 2019
USD ($)
Disclosure of detailed information about financial instruments [line items]        
Carrying value of investment ₨ 1,235 ₨ 1,206   $ 18
Drivestream Inc [member]        
Disclosure of detailed information about financial instruments [line items]        
Ownership interest 43.70% 43.70% 19.00%  
Carrying value of investment ₨ 653 ₨ 630    
Denim Group LLC [member]        
Disclosure of detailed information about financial instruments [line items]        
Ownership interest 33.30% 33.30%    
Carrying value of investment ₨ 582 ₨ 576