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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
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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

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