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Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Net Income (Loss) from Continuing Operations Available to Common Shareholders, Diluted Net Income (Loss) from Continuing Operations Available to Common Shareholders, Diluted Income Tax Contingency [Table] Income Tax Contingency [Table] Machinery and equipment Machinery and Equipment [Member] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount External Credit Rating, Standard & Poor's [Domain] External Credit Rating, Standard & Poor's [Domain] 3.250% Convertible Senior Notes due March 2028 (2028 Convertible Notes) 3.250% Convertible Senior Notes due March 2028 [Member] 3.250% Convertible Senior Notes due March 2028 Executive Category: Executive Category [Axis] LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Costs and expenses Operating Costs and Expenses [Abstract] Corporate and Other Corporate and Other Corporate and Other Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Inventories, net Inventories, net Inventory, Net All Award Types Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Unrealized losses (gains) on foreign currency option contracts Monetization of foreign currency hedge positions Monetization of foreign currency hedge positions Thermal coal Thermal Coal [Member] Thermal Coal [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Guarantees and Product Warranties [Abstract] Anglo American Acquisition Anglo American Acquisition [Member] Anglo American Acquisition Transaction support agreements, additional collateral demands Debt Instrument, Transaction Support Agreement, Additional Collateral Demands Debt Instrument, Transaction Support Agreement, Additional Collateral Demands PEO Name PEO Name Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger Debt Instrument, Principle Amount Debt Instrument, Principle Amount Debt Instrument, Principle Amount Restricted Cash Restricted Cash Property, Plant and Equipment, Type [Axis] Long-Lived Asset, Class [Axis] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Surety Agreement Liquidity Covenant, Amount Surety Agreement Liquidity Covenant, Amount Surety Agreement Liquidity Covenant, Amount Entity Tax Identification Number Entity Tax Identification Number Letter of credit amendment Letter of credit amendment [Member] Letter of credit amendment Collateralized Letter of Credit Agreement Collateralized Letter of Credit Agreement [Member] Collateralized Letter of Credit Agreement Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation, Beginning Balance 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[Domain] Debt Instrument [Axis] Debt Instrument [Axis] Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage Noncash share-based compensation Share-Based Payment Arrangement, Noncash Expense Other Commercial Events [Table] OtherCommercialEvents [Table] Other Commercial Events [Table] Cash paid for interest, net of capitalized interest Interest Paid, Capitalized, Investing Activity Subsegments Consolidation Items [Domain] Subsegments Consolidation Items [Domain] Investment, Name [Domain] Investment, Name [Domain] Schedule of Inventories Schedule of Inventory, Current [Table Text Block] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Basic (loss) income per share Earnings Per Share, Basic Earnings Per Share, Basic Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] Repayments of long-term debt Repayment of Long-Term Debt, Long-Term Lease Obligation, and Capital Security Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Table Text Block] Award Type Award Type [Axis] Additions to property, plant, equipment and mine development Increase (Decrease) in Property, Plant and Equipment, Investing Activities Increase (Decrease) in Property, Plant and Equipment, Investing Activities Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts receivable, net of allowance for credit losses of $0.0 at June 30, 2026 and December 31, 2025 Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Retained earnings Retained Earnings (Accumulated Deficit) Credit facility amendment stage [Domain] Credit facility amendment stage [Domain] Credit facility amendment stage [Domain] Distributions from joint ventures Distributions from joint ventures Distributions from joint ventures Product and Service [Axis] Product and Service [Axis] Initial Conversion Price Premium Price Initial Conversion Price Premium Initial Conversion Price Premium Debt Instrument, Convertible, Threshold Trading Days Debt Instrument, Convertible, Threshold Trading Days Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pension Plan Pension Plan [Member] Common Stock Common Stock [Member] External Credit Rating by Grouping [Axis] External Credit Rating by Grouping [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Former Address Former Address [Member] Reportable segment results Segment Reporting, Operating Income (Loss) [Abstract] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] incremental repair costs Incremental Repair Costs [Member] Incremental Repair Costs Derivative Contract [Domain] Derivative Contract [Domain] Tax provision (benefit) due to remeasurement Remeasurement of income tax Remeasurement of income tax Transfers Between Fair Value Measurement Hierarchy Levels Transfers Between Fair Value Measurement Hierarchy Levels Transfers Between Fair Value Measurement Hierarchy Levels Equity Awards Adjustments Equity Awards Adjustments [Member] Land and coal interests Land and Coal [Member] Land and Coal Letter of Credit Release Letter of Credit Release Letter of Credit Release R3 Renewables II R3 Renewables II [Member] R3 Renewables II Total liabilities and stockholders’ equity Liabilities and Equity Regulatory Asset [Domain] Regulatory Asset [Domain] Other revenue Other revenue [Member] Other revenue Employee Stock Option Share-Based Payment Arrangement, Option [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Noncontrolling interests Equity, Attributable to Noncontrolling Interest Debt Instrument, Funded, Percent Debt Instrument, Funded, Percent Debt outstanding deemed to be funded Segments [Axis] Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Mine Location [Domain] Mine Location [Domain] [Domain] for Mine Location [Axis] Related Party [Domain] Related and Nonrelated Parties [Domain] Restructuring charges Restructuring charges Restructuring Charges Underlying Asset Class [Domain] Underlying Asset Class [Domain] Geographic Distribution [Domain] Geographic Distribution [Domain] Schedule of Accounts Receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Income Tax Authority [Domain] Income Tax Jurisdiction [Domain] Inventory Disclosure [Abstract] Inventory Disclosure [Abstract] Tabular List, Table Tabular List [Table 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Disclosure [Text Block] Income Tax Disclosure [Text Block] Debt instrument, fronting fee Debt instrument, fronting fee Debt instrument, fronting fee Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Credit agreement pricing stage [Axis] Credit agreement pricing stage [Axis] Credit agreement pricing stage Debt Instrument [Line Items] Debt Instrument [Line Items] Other current assets Increase (Decrease) in Other Current Assets Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Corporate and Other (1) Corporate Segment and Other Operating Segment [Member] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Additional paid-in capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Payment of Capped Call Transactions Payment of Capped Call Transactions Payment of Capped Call Transactions 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At-Risk for Impairment of Long-Lived Assets Held and Used [Line Items] Long-Lived Asset, Held and Used, Impairment [Line Items] Dividends [Axis] Dividends [Axis] Revision of Prior Period [Axis] Revision of Prior Period [Axis] Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and Cash Equivalent Comprehensive loss attributable to common stockholders Comprehensive Income (Loss) Attributable to Common Stockholders Comprehensive Income (Loss) Attributable to Common Stockholders Repair costs Repair costs Repair costs Company Selected Measure Amount Company Selected Measure Amount Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] Depreciation, depletion and amortization Depreciation, depletion and amortization Depreciation, Depletion and Amortization Total Letters of Credit in Support of Surety Bonds Total Letters of Credit in Support of Surety Bonds Total Letters of Credit in Support of Surety Bonds (Loss) 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property, plant, equipment and mine development excluding corporate and other segment Additions to property, plant, equipment and mine development excluding corporate and other segment Arbitration Relating to Terminated Anglo American Acquisition Arbitration Relating to Terminated Anglo American Acquisition [Member] Arbitration Relating to Terminated Anglo American Acquisition Award Timing Method Award Timing Method [Text Block] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Total Surety Bonds and Letters of Credit Outstanding Total Surety Bonds and Letters of Credit Outstanding Total Surety Bonds and Letters of Credit Outstanding Net change in cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Collateral amount held in letters of credit Collateral amount held as letters of credit Collateral amount held as letters of credit Asset Retirement Obligations Asset Retirement Obligations [Member] Asset Retirement Obligations Debt Instrument, Convertible, Revised Conversion Ratio Debt Instrument, Convertible, Revised Conversion Ratio Debt Instrument, Convertible, Revised Conversion Ratio LC Facility LC Facility [Member] LC Facility Newly Adopted Accounting Standards and Accounting Standards Not Yet Implemented Accounting Standards Update and Change in Accounting Principle [Text Block] Returned deposit related to terminated acquisition Returned deposit related to terminated acquisition Returned deposit related to terminated acquisition Net (loss) income attributable to common stockholders Net Income (Loss) Attributable to Parent Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Less: Unamortized debt issuance costs Unamortized Debt Issuance Expense Unamortized Debt Issuance Expense Middlemount Mine Middlemount Mine Middlemount Mine [Member] Middlemount Mine [Member] Proceeds from disposal of assets, net of receivables Proceeds from Sale of Property, Plant, and Equipment Statement [Table] Statement [Table] Loss from discontinued operations, net of income taxes Loss from discontinued operations, net of income taxes Loss from discontinued operations, net of income taxes Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Workers’ compensation obligations Increase (Decrease) in Workers' Compensation Liabilities Restatement Determination Date: Restatement Determination Date [Axis] Trading Activity [Axis] Trading Activity [Axis] Interest income Interest income Investment Income, Interest Proceeds from Buma loan note Proceeds from Notes Payable Upfront cash payment for planned acquisition Upfront cash payment for planned acquisition Upfront cash payment for planned acquisition Credit Rating, Standard & Poor's [Axis] Credit Rating, Standard & Poor's [Axis] Debt Instrument, Convertible, Threshold Consecutive Trading Days Debt Instrument, Convertible, Threshold Consecutive Trading Days Derivative Asset, Fair Value, Gross Asset Derivative Asset, Subject to Master Netting Arrangement, before Offset Powder River Basin Powder River Basin Mining [Member] Powder River Basin Mining [Member] Interest rate basis [Axis] Interest rate basis [Axis] Interest rate basis Geographic Distribution [Axis] Geographic Distribution [Axis] Loss Contingency, Damages Sought, Value Loss Contingency, Damages Sought, Value Long-term Purchase Commitment by Category of Item Purchased [Axis] Category of Item Purchased [Axis] Accrued postretirement benefit costs Liability, Other Postretirement Defined Benefit Plan, Noncurrent Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Diluted EPS numerator: Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract]