Related party disclosures - Additional Information (Detail) € in Thousands	12 Months Ended
Dec. 31, 2025 EUR (€) shares
Disclosure of transactions between related parties [line items]
Amounts payable, related party transactions \| €	€ 0
Directors and executive officers [Member]
Disclosure of transactions between related parties [line items]
Number of share options forfeited in share-based payment arrangement	0
Key management personnel of entity or parent [member] \| Service Options [Member] \| Immatics GmbH [Member]
Disclosure of transactions between related parties [line items]
Number of share options granted in share-based payment arrangement	561,000

The amounts payable resulting from related party transactions. [Refer: Total for all related parties [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2025-01-01
-Paragraph 20
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=24&code=ifrs-tx-2025-en-r&anchor=para_20&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2025-01-01
-Paragraph 18
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=24&code=ifrs-tx-2025-en-r&anchor=para_18_b&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 230
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_230_b&doctype=Standard
-URIDate 2025-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 230
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_230_b&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_AmountsPayableRelatedPartyTransactions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant