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Financial Instruments - Summary of Aggregate Contracted Principal Amounts of Company's Derivative Contracts Outstanding (Parenthetical) (Detail)
₨ in Millions, $ in Millions
Mar. 31, 2020
INR (₨)
Mar. 31, 2020
USD ($)
Mar. 31, 2019
INR (₨)
Mar. 31, 2019
USD ($)
At fair value [member]        
Disclosure of derivative contract outstanding [line items]        
Non-designated derivative instruments | ₨ ₨ (4,344)   ₨ 3,794  
At fair value [member] | Philippines, Pesos | Sell: Forward contracts [member]        
Disclosure of derivative contract outstanding [line items]        
Non-designated derivative instruments   $ 176    
At fair value [member] | Top of range [member]        
Disclosure of derivative contract outstanding [line items]        
Designated derivative instruments | ₨ ₨ 1      
At cost [member] | Sell: Forward contracts [member]        
Disclosure of derivative contract outstanding [line items]        
Non-designated derivative instruments   $ 1,314   $ 1,182
At cost [member] | Philippines, Pesos | Sell: Forward contracts [member]        
Disclosure of derivative contract outstanding [line items]        
Non-designated derivative instruments       $ 117