Income taxes - Narrative (Details) SFr in Millions	12 Months Ended
Dec. 31, 2025 CHF (SFr)
Income Taxes [Abstract]
Current tax expense (income), related to pillar two income taxes	SFr 0.9

The amount of current tax expense (income) related to Pillar Two income taxes.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2025-01-01
-Paragraph 88B
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2025-en-r&anchor=para_88B&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 197
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_197&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 197
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_197&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_CurrentTaxExpenseIncomeRelatedToPillarTwoIncomeTaxes
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration