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Employee Benefits - Additional Information (Detail) - INR (₨)
₨ in Millions
Mar. 31, 2018
Mar. 31, 2017
Actuarial assumption of discount rates [member]    
Disclosure of defined benefit plans [line items]    
Percentage of reasonably possible increase in actuarial assumption 0.50% 0.50%
Percentage of reasonably possible decrease in actuarial assumption 0.50% 0.50%
Increase/ (decrease) in gratuity benefit obligation due to reasonably possible increase in actuarial assumption ₨ 341 ₨ 207
Increase/ (decrease) in gratuity benefit obligation due to reasonably possible decrease in actuarial assumption ₨ (320) ₨ (187)
Actuarial assumption of expected rates of salary increases [member]    
Disclosure of defined benefit plans [line items]    
Percentage of reasonably possible increase in actuarial assumption 0.50% 0.50%
Percentage of reasonably possible decrease in actuarial assumption 0.50% 0.50%
Increase/ (decrease) in gratuity benefit obligation due to reasonably possible increase in actuarial assumption ₨ 184 ₨ 176
Increase/ (decrease) in gratuity benefit obligation due to reasonably possible decrease in actuarial assumption ₨ (173) ₨ (169)