Related party disclosure - Summary of Detailed Information About Related Parties Explanatory (Detail)	12 Months Ended
Mar. 31, 2026
Fluence India ReNew JV Private Limited
Disclosure Of Detailed Information About Related Parties [Line Items]
Name Of Joint Venture	Fluence India ReNew JV Private Limited
Entities Owned Or Significantly Influenced By Key Management Personnel \| ReNew Foundation
Disclosure Of Detailed Information About Related Parties [Line Items]
Name Of Entities Owned Or Significantly Influenced By Key Management Personnel Or Their Relatives	ReNew Foundation

The name of a joint venture. [Refer: Total for all joint ventures [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2025-01-01
-Paragraph 17
-Subparagraph b
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2025-en-r&anchor=para_17_b_i&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2025-01-01
-Paragraph 16
-Subparagraph b
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2025-en-r&anchor=para_16_b_i&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2025-01-01
-Paragraph 21
-Subparagraph a
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2025-en-r&anchor=para_21_a_i&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_NameOfJointVenture
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration