Summary of significant accounting policies - Impairment for Long-lived Assets (Details) - USD ($)	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Accounting Policies [Abstract]
Impairment of long-lived assets	$ 0	$ 0

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
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Name:	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration