Financial Instruments - Details of Guarantees and Documentary Credits Outstanding (Detail) ₨ in Millions, $ in Millions	Mar. 31, 2026 INR (₨)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 INR (₨)
Guarantor Obligations [Line Items]
Bank guarantees	₨ 2,913,117.7	$ 31,046.8	₨ 2,462,279.4
Estimated fair value	(17,060.2)	(181.9)	(12,875.5)
Financial guarantees
Guarantor Obligations [Line Items]
Bank guarantees	925,004.9	9,858.3	714,278.7
Performance guarantees
Guarantor Obligations [Line Items]
Bank guarantees	969,271.9	10,330.1	781,152.1
Documentary credits
Guarantor Obligations [Line Items]
Bank guarantees	1,018,840.9	10,858.4	966,848.6
Estimated fair value	(1,524.8)	(16.3)	(1,462.5)
Guarantees [Member]
Guarantor Obligations [Line Items]
Estimated fair value	₨ (15,535.4)	$ (165.6)	₨ (11,413.0)

Fair value portion of guarantee, including, but not limited to, financial standby letter of credit, fair value guarantee, guarantee of collection of scheduled contractual cash flows from financial assets, and contracts that contingently require the guarantor to make payments or perform services.