Contract liabilities (Details) $ in Thousands	Sep. 30, 2026 USD ($) mill	Dec. 31, 2025 USD ($)
Long-Lived Assets Held-for-sale [Line Items]
Net contract liabilities	$ 4,500
Contract liabilities	$ 4,150	$ 0
Semi-Autogenous Mill
Long-Lived Assets Held-for-sale [Line Items]
Number of mills \| mill	1

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 8
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483467/210-10-45-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-11

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
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-Section 45
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
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-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant