Financial instruments - Aggregate Notional Principal Amounts of Bank's Outstanding Forward Exchange and Derivative Contracts (Detail) ₨ in Millions, $ in Millions	Mar. 31, 2026 INR (₨)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 INR (₨)
Derivatives, Fair Value [Line Items]
Notional	₨ 31,675,575.2	$ 337,584.7	₨ 24,496,285.6
Gross Assets	624,206.5	6,652.4	179,812.4
Gross Liabilities	578,276.3	6,162.9	143,566.1
Net Fair Value	45,930.2	489.5	36,246.3
Interest rate derivatives
Derivatives, Fair Value [Line Items]
Notional	8,467,050.6	90,238.2	10,191,133.7
Gross Assets	51,288.9		58,654.3
Gross Liabilities	61,564.1		48,979.2
Net Fair Value	(10,275.2)	(109.5)	9,675.1
Forward rate agreements
Derivatives, Fair Value [Line Items]
Notional	550,017.3	5,861.8	615,831.9
Gross Assets	6,429.2		15,507.0
Gross Liabilities	19,397.2		5,676.8
Net Fair Value	(12,968.0)	(138.2)	9,830.2
Currency options
Derivatives, Fair Value [Line Items]
Notional	177,937.4	1,896.4	291,621.4
Gross Assets	2,555.9		1,065.3
Gross Liabilities	2,633.3		1,332.6
Net Fair Value	(77.4)	(0.8)	(267.3)
Currency swaps
Derivatives, Fair Value [Line Items]
Notional	385,664.3	4,110.2	462,773.9
Gross Assets	38,377.7		19,180.2
Gross Liabilities	10,715.0		4,360.8
Net Fair Value	27,662.7	294.8	14,819.4
Forward exchange contracts
Derivatives, Fair Value [Line Items]
Notional	22,094,905.6	235,478.1	12,934,924.7
Gross Assets	525,554.8		85,405.6
Gross Liabilities	483,966.7		83,216.7
Net Fair Value	₨ 41,588.1	$ 443.2	₨ 2,188.9

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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