Commitments and contingencies (Details) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2026	Dec. 31, 2025
Commitments and contingencies.
Provision for contingent losses	$ 0	$ 0

Amount of loss (reversal of loss) recognized for loss contingency liability. Includes, but is not limited to, effect of revision in previously reported estimate.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-22

Name:	us-gaap_LossContingencyLossInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration