Lease Liabilities (Details) - Office and laboratory facilities at Zernikedreef in Leiden, the Netherlands € in Thousands		1 Months Ended	6 Months Ended
Jul. 01, 2020	Dec. 31, 2020	Jun. 30, 2025 EUR (€) m²	Dec. 31, 2024 EUR (€)
Disclosure of quantitative information about right-of-use assets [line items]
Area under lease \| m²			4,818
Lease term	10 years	11 years
Lease extension term		1 year
Lease, current extension period under option			5 years
Right-of-use asset \| €			€ 10,903	€ 11,433

The amount of assets that represent a lessee's right to use an underlying asset for the lease term that do not meet the definition of investment property. Underlying asset is an asset that is the subject of a lease, for which the right to use that asset has been provided by a lessor to a lessee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2024-01-01
-Paragraph 53
-Subparagraph j
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2024-en-r&anchor=para_53_j&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 16
-IssueDate 2024-01-01
-Paragraph 47
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=16&code=ifrs-tx-2024-en-r&anchor=para_47_a&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_RightofuseAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant