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Income Taxes - Additional Information (Detail)
₨ / shares in Units, ₨ in Millions, $ in Millions
 12 Months Ended
Mar. 31, 2019
INR (₨)
₨ / shares
Mar. 31, 2018
INR (₨)
₨ / shares
Mar. 31, 2017
INR (₨)
₨ / shares
Mar. 31, 2019
USD ($)
Disclosure of income tax expense [line items]        
Reversal of provisions pertaining to earlier periods ₨ 2,267 ₨ 380 ₨ 593  
Deferred tax asset of unused tax losses not recognized 6,769 3,756    
Tax loss carry-forwards 24,355 14,510    
Tax loss carry-forwards not currently subject to expiration dates 8,191 6,223    
Tax loss carry-forwards expires in various years ₨ 16,164 8,287    
Tax loss carry-forwards expiration period 2038      
Deferred tax asset of unused tax losses recognized ₨ 5,604 6,908   $ 81
Minimum alternate tax 0 74    
Decrease of current tax expense due to tax holidays ₨ 15,390 ₨ 11,635 ₨ 11,958  
Tax incentives per share | ₨ / shares ₨ 2.56 ₨ 1.84 ₨ 1.85  
Deferred tax liabilities on cumulative earnings of subsidiaries ₨ 52,488 ₨ 51,432    
Branch profit tax percentage 15.00%      
Unused tax losses [member]        
Disclosure of income tax expense [line items]        
Deferred tax asset of unused tax losses recognized ₨ 3,149 ₨ 5,694