Income Taxes - Additional Information (Detail) ₨ in Millions, $ in Millions	Mar. 31, 2020 INR (₨)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 INR (₨)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 INR (₨)
Income Taxes [Line Items]
Total unrecognized tax benefit	₨ 37,103.2	$ 492.1	₨ 14,448.1	$ 191.6	₨ 648.3
The total unrecognized tax benefits, if recognized, that would reduce the tax and thereby affect the effective tax rate	₨ 37,103.2
Income tax rate including surcharge and education cess	25.17%	25.17%

Amount of unrecognized tax benefits.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 10B
-URI http://asc.fasb.org/extlink&oid=120406818&loc=SL37586934-109318

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

Name:	us-gaap_UnrecognizedTaxBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant