Retirement benefits - Assumptions Used in Accounting for Gratuity Plan (Detail) - Gratuity |
12 Months Ended | ||||
|---|---|---|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
Mar. 31, 2023 |
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| Minimum | |||||
| Defined Benefit Plan Disclosure [Line Items] | |||||
| Discount rate - net periodic benefit cost | [1] | 6.50% | 7.20% | 5.10% | |
| Rate of increase in compensation levels of covered employees | 4.00% | 3.00% | 6.00% | ||
| Rate of return on plan assets | 6.50% | 6.50% | 5.10% | ||
| Maximum | |||||
| Defined Benefit Plan Disclosure [Line Items] | |||||
| Discount rate - net periodic benefit cost | [1] | 8.10% | 8.30% | 7.90% | |
| Rate of increase in compensation levels of covered employees | 14.00% | 15.00% | 11.00% | ||
| Rate of return on plan assets | 7.00% | 7.40% | 7.20% | ||
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