Portfolio of Available for Sale Debt Securities (Detail) ₨ in Millions, $ in Millions	Mar. 31, 2022 INR (₨)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 INR (₨)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	₨ 4,416,934.2	$ 58,217.1	₨ 4,241,981.6
Gross Unrealized Gains	22,472.3	296.2	57,061.0
Gross Unrealized Losses	50,843.4	670.1	23,592.7
Fair Value	4,388,563.1	57,843.2	4,275,449.9
Debt securities, other than asset and mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,273,955.4		4,084,551.2
Gross Unrealized Gains	20,952.7		52,977.7
Gross Unrealized Losses	50,262.6		23,281.0
Fair Value	4,244,645.5	$ 55,946.3	4,114,247.9
Debt securities, other than asset and mortgage-backed securities \| Government of India securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,226,917.6		3,159,905.2
Gross Unrealized Gains	10,995.6		31,824.6
Gross Unrealized Losses	42,946.3		20,225.8
Fair Value	3,194,966.9		3,171,504.0
Debt securities, other than asset and mortgage-backed securities \| State government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	429,146.8		348,067.7
Gross Unrealized Gains	4,395.9		7,373.7
Gross Unrealized Losses	5,865.9		2,669.6
Fair Value	427,676.8		352,771.8
Debt securities, other than asset and mortgage-backed securities \| Government securities outside India
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,279.2		5,932.2
Gross Unrealized Gains	0.0		3.8
Gross Unrealized Losses	3.4		0.0
Fair Value	2,275.8		5,936.0
Debt securities, other than asset and mortgage-backed securities \| Credit Substitutes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	578,922.3		534,227.1
Gross Unrealized Gains	5,381.4		13,423.1
Gross Unrealized Losses	1,283.5		373.3
Fair Value	583,020.2		547,276.9
Debt securities, other than asset and mortgage-backed securities \| Other corporate/financial institution bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	36,689.5		36,419.0
Gross Unrealized Gains	179.8		352.5
Gross Unrealized Losses	163.5		12.3
Fair Value	36,705.8		36,759.2
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	24.2		30.5
Gross Unrealized Gains	0.0		1.8
Gross Unrealized Losses	1.3		0.0
Fair Value	22.9		32.3
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	142,954.6		157,399.9
Gross Unrealized Gains	1,519.6		4,081.5
Gross Unrealized Losses	579.5		311.7
Fair Value	143,894.7		161,169.7
Securities with gross unrealized losses
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,791,389.0		1,162,099.9
Securities with gross unrealized gains
Schedule of Available-for-sale Securities [Line Items]
Fair Value	₨ 2,597,174.1		₨ 3,113,350.0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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