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Stock Options Outstanding, Employees Stock Option Schemes (Detail) - Employees Stock Option Scheme
12 Months Ended
Mar. 31, 2018
₨ / shares
shares
Mar. 31, 2018
₨ / shares
$ / shares
shares
Mar. 31, 2017
₨ / shares
shares
Mar. 31, 2016
₨ / shares
shares
Mar. 31, 2015
₨ / shares
shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Number Of Shares Arising Out Of Options | shares 75,443,800 75,443,800 92,156,300 128,654,300 109,033,000
Weighted Average Exercise Price ₨ 1,050.22 ₨ 1,050.22 ₨ 904.97 ₨ 840.19 ₨ 683.16
Plan ''C''          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Range of exercise price, Lower Range | (per share) 680.0 ₨ 10.44      
Range of exercise price, Upper Range | (per share) ₨ 835.50 ₨ 12.83      
Number Of Shares Arising Out Of Options | shares 3,261,500 3,261,500      
Weighted Average Remaining Life 1 year 3 months 25 days 1 year 3 months 25 days      
Weighted Average Exercise Price ₨ 685.72 ₨ 685.72      
Plan ''D''          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Range of exercise price | (per share) ₨ 680 ₨ 10.44      
Number Of Shares Arising Out Of Options | shares 1,635,700 1,635,700      
Weighted Average Remaining Life 1 year 5 months 4 days 1 year 5 months 4 days      
Weighted Average Exercise Price ₨ 680.00 ₨ 680.00      
Plan "E"          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Range of exercise price | $ / shares   ₨ 10.44      
Range of exercise price, Lower Range ₨ 680.0        
Number Of Shares Arising Out Of Options | shares 6,224,900 6,224,900      
Weighted Average Remaining Life 1 year 6 months 3 days 1 year 6 months 3 days      
Weighted Average Exercise Price ₨ 680.00 ₨ 680.00      
Plan "F"          
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]          
Range of exercise price, Lower Range | (per share) 835.5 ₨ 12.83      
Range of exercise price, Upper Range | (per share) ₨ 1,462.15 ₨ 22.46      
Number Of Shares Arising Out Of Options | shares 64,321,700 64,321,700      
Weighted Average Remaining Life 3 years 7 months 2 days 3 years 7 months 2 days      
Weighted Average Exercise Price ₨ 1,113.95 ₨ 1,113.95