Employment benefit plans - Summary of Defined Benefit Plan Liability Recognized in Statement of Financial Position (Detail) - Defined Benefit Gratuity Plan [Member] ₨ in Millions, $ in Millions	Mar. 31, 2026 INR (₨)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 INR (₨)	Mar. 31, 2025 USD ($)	Mar. 31, 2024 INR (₨)	Mar. 31, 2023 INR (₨)
Defined benefit liability
Present value of unfunded obligation	₨ 532	$ 6	₨ 315
Net liability	₨ 532	$ 6	₨ 315	$ 3	₨ 300	₨ 231

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [domain]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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