Restricted cash - Components of Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Restricted Cash and Cash Equivalent Item [Line Items]
Total	$ 22,493	$ 27,498
Reclamation and other surety bond cash collateral
Restricted Cash and Cash Equivalent Item [Line Items]
Total	22,439	27,445
Credit card collateral
Restricted Cash and Cash Equivalent Item [Line Items]
Total	$ 54	$ 53

Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-SubTopic 210
-Topic 954
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477220/954-210-45-5

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-8

Name:	us-gaap_RestrictedCashNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant