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Movement in Provision for Credit Card and Debit Card Reward Points (Detail) - Debit and Credit Cards Reward Points
₨ in Millions, $ in Millions
 12 Months Ended
Mar. 31, 2018
INR (₨)
Mar. 31, 2018
USD ($)
Mar. 31, 2017
INR (₨)
Valuation and Qualifying Accounts Disclosure [Line Items]      
Opening provision of reward points ₨ 4,312.4 $ 66.2 ₨ 3,063.6
Provision made during the year 2,650.9 40.7 2,786.8
Utilization/write back of provision (2,220.7) (34.1) (2,093.6)
Closing provision of reward points 4,711.2 72.3 4,312.4
Change in Rate of Accrual of Reward Points      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Effect of change in rate of accrual of points/cost of reward 1.3 0.0 242.8
Change in Cost of Reward Points      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Effect of change in rate of accrual of points/cost of reward ₨ (32.7) $ (0.5) ₨ 312.8