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Summary of significant accounting policies - Computation of Depreciation of Property and Equipment (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2024
Property Plant And Equipment [Line Items] |  |
Asset impairment charges | $ 3.8 |
Buildings and improvements | Minimum |  |
Property Plant And Equipment [Line Items] |  |
Property and equipment useful life |  | 10 years
Buildings and improvements | Maximum |  |
Property Plant And Equipment [Line Items] |  |
Property and equipment useful life |  | 40 years
Machinery and equipment | Minimum |  |
Property Plant And Equipment [Line Items] |  |
Property and equipment useful life |  | 3 years
Machinery and equipment | Maximum |  |
Property Plant And Equipment [Line Items] |  |
Property and equipment useful life |  | 20 years
Mine development costs |  |
Property Plant And Equipment [Line Items] |  |
Property and equipment useful life |  | us-gaap:UnitsOfProductionDepreciationMethodMember

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- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482130/360-10-45-4 + Details
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- Definition Indicates method of allocating cost over useful life in systematic and rational manner for property, plant, and equipment. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 360 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482099/360-10-50-1 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 7A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A + Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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