Financial Instruments - Summary of Aggregate Contracted Principal Amounts of Company's Derivative Contracts Outstanding (Parenthetical) (Detail) ₱ in Millions, ₨ in Millions, $ in Millions	Mar. 31, 2026 INR (₨)	Mar. 31, 2026 USD ($)	Mar. 31, 2026 PHP (₱)	Mar. 31, 2025 INR (₨)	Mar. 31, 2025 USD ($)	Mar. 31, 2025 PHP (₱)
At fair value [member]
Disclosure of derivative contract outstanding [line items]
Non-designated derivative instruments	₨ (10,090)			₨ 852
At fair value [member] \| Philippines, Pesos [member] \| Sell: Forward contracts [member]
Disclosure of derivative contract outstanding [line items]
Non-designated derivative instruments	₨ 0			₨ (4)
At cost [member] \| Sell: Forward contracts [member]
Disclosure of derivative contract outstanding [line items]
Non-designated derivative instruments \| $		$ 944			$ 752
At cost [member] \| Philippines, Pesos [member] \| Sell: Forward contracts [member]
Disclosure of derivative contract outstanding [line items]
Non-designated derivative instruments		$ 242	₱ 0		$ 197	₱ 150