3.21.1 html 87 283 1 false 43 0 false 6 false false R1.htm 0001001 - Document - Cover Page Sheet http://www.warriormetcoal.com/role/CoverPage Cover Page Cover 1 false false R2.htm 1001002 - Statement - CONDENSED STATEMENTS OF OPERATIONS Sheet http://www.warriormetcoal.com/role/CONDENSEDSTATEMENTSOFOPERATIONS CONDENSED STATEMENTS OF OPERATIONS Statements 2 false false R3.htm 1002003 - Statement - CONDENSED BALANCE SHEETS Sheet http://www.warriormetcoal.com/role/CONDENSEDBALANCESHEETS CONDENSED BALANCE SHEETS Statements 3 false false R4.htm 1003004 - Statement - CONDENSED BALANCE SHEETS (Parenthetical) Sheet http://www.warriormetcoal.com/role/CONDENSEDBALANCESHEETSParenthetical CONDENSED BALANCE SHEETS (Parenthetical) Statements 4 false false R5.htm 1004005 - Statement - CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY Sheet http://www.warriormetcoal.com/role/CONDENSEDSTATEMENTSOFCHANGESINSTOCKHOLDERSEQUITY CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY Statements 5 false false R6.htm 1005006 - Statement - CONDENSED STATEMENTS OF CASH FLOWS Sheet http://www.warriormetcoal.com/role/CONDENSEDSTATEMENTSOFCASHFLOWS CONDENSED STATEMENTS OF CASH FLOWS Statements 6 false false R7.htm 2101101 - Disclosure - Business and Basis of Presentation Sheet http://www.warriormetcoal.com/role/BusinessandBasisofPresentation Business and Basis of Presentation Notes 7 false false R8.htm 2102102 - Disclosure - Summary of Significant Accounting Policies Sheet http://www.warriormetcoal.com/role/SummaryofSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 8 false false R9.htm 2106103 - Disclosure - Inventories, net Sheet http://www.warriormetcoal.com/role/Inventoriesnet Inventories, net Notes 9 false false R10.htm 2109104 - Disclosure - Income Taxes Sheet http://www.warriormetcoal.com/role/IncomeTaxes Income Taxes Notes 10 false false R11.htm 2113105 - Disclosure - Debt Sheet http://www.warriormetcoal.com/role/Debt Debt Notes 11 false false R12.htm 2117106 - Disclosure - Other Long-Term Liabilities Sheet http://www.warriormetcoal.com/role/OtherLongTermLiabilities Other Long-Term Liabilities Notes 12 false false R13.htm 2120107 - Disclosure - Leases Sheet http://www.warriormetcoal.com/role/Leases Leases Notes 13 false false R14.htm 2127108 - Disclosure - Net (Loss) Income per Share Sheet http://www.warriormetcoal.com/role/NetLossIncomeperShare Net (Loss) Income per Share Notes 14 false false R15.htm 2131109 - Disclosure - Related Party Transactions Sheet http://www.warriormetcoal.com/role/RelatedPartyTransactions Related Party Transactions Notes 15 false false R16.htm 2133110 - Disclosure - Commitments and Contingencies Sheet http://www.warriormetcoal.com/role/CommitmentsandContingencies Commitments and Contingencies Notes 16 false false R17.htm 2135111 - Disclosure - Stockholders' Equity Sheet http://www.warriormetcoal.com/role/StockholdersEquity Stockholders' Equity Notes 17 false false R18.htm 2137112 - Disclosure - Fair Value of Financial Instruments Sheet http://www.warriormetcoal.com/role/FairValueofFinancialInstruments Fair Value of Financial Instruments Notes 18 false false R19.htm 2139113 - Disclosure - Segment Information Sheet http://www.warriormetcoal.com/role/SegmentInformation Segment Information Notes 19 false false R20.htm 2145114 - Disclosure - Subsequent Events Sheet http://www.warriormetcoal.com/role/SubsequentEvents Subsequent Events Notes 20 false false R21.htm 2203201 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://www.warriormetcoal.com/role/SummaryofSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://www.warriormetcoal.com/role/SummaryofSignificantAccountingPolicies 21 false false R22.htm 2307301 - Disclosure - Inventories, net (Tables) Sheet http://www.warriormetcoal.com/role/InventoriesnetTables Inventories, net (Tables) Tables http://www.warriormetcoal.com/role/Inventoriesnet 22 false false R23.htm 2310302 - Disclosure - Income Taxes (Tables) Sheet http://www.warriormetcoal.com/role/IncomeTaxesTables Income Taxes (Tables) Tables http://www.warriormetcoal.com/role/IncomeTaxes 23 false false R24.htm 2314303 - Disclosure - Debt (Tables) Sheet http://www.warriormetcoal.com/role/DebtTables Debt (Tables) Tables http://www.warriormetcoal.com/role/Debt 24 false false R25.htm 2318304 - Disclosure - Other Long-Term Liabilities (Tables) Sheet http://www.warriormetcoal.com/role/OtherLongTermLiabilitiesTables Other Long-Term Liabilities (Tables) Tables http://www.warriormetcoal.com/role/OtherLongTermLiabilities 25 false false R26.htm 2321305 - Disclosure - Leases (Tables) Sheet http://www.warriormetcoal.com/role/LeasesTables Leases (Tables) Tables http://www.warriormetcoal.com/role/Leases 26 false false R27.htm 2328306 - Disclosure - Net (Loss) Income per Share (Tables) Sheet http://www.warriormetcoal.com/role/NetLossIncomeperShareTables Net (Loss) Income per Share (Tables) Tables http://www.warriormetcoal.com/role/NetLossIncomeperShare 27 false false R28.htm 2340307 - Disclosure - Segment Information (Tables) Sheet http://www.warriormetcoal.com/role/SegmentInformationTables Segment Information (Tables) Tables http://www.warriormetcoal.com/role/SegmentInformation 28 false false R29.htm 2404401 - Disclosure - Summary of Significant Accounting Policies - Short-Term Investments (Details) Sheet http://www.warriormetcoal.com/role/SummaryofSignificantAccountingPoliciesShortTermInvestmentsDetails Summary of Significant Accounting Policies - Short-Term Investments (Details) Details 29 false false R30.htm 2405402 - Disclosure - Summary of Significant Accounting Policies - Revenue Recognition (Details) Sheet http://www.warriormetcoal.com/role/SummaryofSignificantAccountingPoliciesRevenueRecognitionDetails Summary of Significant Accounting Policies - Revenue Recognition (Details) Details 30 false false R31.htm 2408403 - Disclosure - Inventories, net (Details) Sheet http://www.warriormetcoal.com/role/InventoriesnetDetails Inventories, net (Details) Details http://www.warriormetcoal.com/role/InventoriesnetTables 31 false false R32.htm 2411404 - Disclosure - Income Taxes- Narrative (Details) Sheet http://www.warriormetcoal.com/role/IncomeTaxesNarrativeDetails Income Taxes- Narrative (Details) Details 32 false false R33.htm 2412405 - Disclosure - Income Taxes - Valuation Allowance Schedule (Details) Sheet http://www.warriormetcoal.com/role/IncomeTaxesValuationAllowanceScheduleDetails Income Taxes - Valuation Allowance Schedule (Details) Details 33 false false R34.htm 2415406 - Disclosure - Debt - Schedule of Long-Term Debt (Details) Sheet http://www.warriormetcoal.com/role/DebtScheduleofLongTermDebtDetails Debt - Schedule of Long-Term Debt (Details) Details 34 false false R35.htm 2416407 - Disclosure - Debt - Narrative (Details) Sheet http://www.warriormetcoal.com/role/DebtNarrativeDetails Debt - Narrative (Details) Details 35 false false R36.htm 2419408 - Disclosure - Other Long-Term Liabilities (Details) Sheet http://www.warriormetcoal.com/role/OtherLongTermLiabilitiesDetails Other Long-Term Liabilities (Details) Details http://www.warriormetcoal.com/role/OtherLongTermLiabilitiesTables 36 false false R37.htm 2422409 - Disclosure - Leases - Narrative (Details) Sheet http://www.warriormetcoal.com/role/LeasesNarrativeDetails Leases - Narrative (Details) Details 37 false false R38.htm 2423410 - Disclosure - Leases - Supplemental Balance Sheet Information (Details) Sheet http://www.warriormetcoal.com/role/LeasesSupplementalBalanceSheetInformationDetails Leases - Supplemental Balance Sheet Information (Details) Details 38 false false R39.htm 2424411 - Disclosure - Leases - Components of Lease Expense (Details) Sheet http://www.warriormetcoal.com/role/LeasesComponentsofLeaseExpenseDetails Leases - Components of Lease Expense (Details) Details 39 false false R40.htm 2425412 - Disclosure - Leases - Maturities of Lease Liabilities (Details) Sheet http://www.warriormetcoal.com/role/LeasesMaturitiesofLeaseLiabilitiesDetails Leases - Maturities of Lease Liabilities (Details) Details 40 false false R41.htm 2426413 - Disclosure - Leases - Supplemental Cash Flow Information (Details) Sheet http://www.warriormetcoal.com/role/LeasesSupplementalCashFlowInformationDetails Leases - Supplemental Cash Flow Information (Details) Details 41 false false R42.htm 2429414 - Disclosure - Net (Loss) Income per Share - Schedule of Earnings per Share (Details) Sheet http://www.warriormetcoal.com/role/NetLossIncomeperShareScheduleofEarningsperShareDetails Net (Loss) Income per Share - Schedule of Earnings per Share (Details) Details http://www.warriormetcoal.com/role/NetLossIncomeperShareTables 42 false false R43.htm 2430415 - Disclosure - Net (Loss) Income per Share - Narrative (Details) Sheet http://www.warriormetcoal.com/role/NetLossIncomeperShareNarrativeDetails Net (Loss) Income per Share - Narrative (Details) Details http://www.warriormetcoal.com/role/NetLossIncomeperShareTables 43 false false R44.htm 2432416 - Disclosure - Related Party Transactions - Narrative (Details) Sheet http://www.warriormetcoal.com/role/RelatedPartyTransactionsNarrativeDetails Related Party Transactions - Narrative (Details) Details 44 false false R45.htm 2434417 - Disclosure - Commitments and Contingencies - Narrative (Details) Sheet http://www.warriormetcoal.com/role/CommitmentsandContingenciesNarrativeDetails Commitments and Contingencies - Narrative (Details) Details 45 false false R46.htm 2436418 - Disclosure - Stockholders' Equity (Details) Sheet http://www.warriormetcoal.com/role/StockholdersEquityDetails Stockholders' Equity (Details) Details http://www.warriormetcoal.com/role/StockholdersEquity 46 false false R47.htm 2438419 - Disclosure - Fair Value of Financial Instruments (Details) Sheet http://www.warriormetcoal.com/role/FairValueofFinancialInstrumentsDetails Fair Value of Financial Instruments (Details) Details http://www.warriormetcoal.com/role/FairValueofFinancialInstruments 47 false false R48.htm 2441420 - Disclosure - Segment Information - Narrative (Details) Sheet http://www.warriormetcoal.com/role/SegmentInformationNarrativeDetails Segment Information - Narrative (Details) Details 48 false false R49.htm 2442421 - Disclosure - Segment Information - Reconciliation of Revenue (Details) Sheet http://www.warriormetcoal.com/role/SegmentInformationReconciliationofRevenueDetails Segment Information - Reconciliation of Revenue (Details) Details 49 false false R50.htm 2443422 - Disclosure - Segment Information - Reconciliation of Capital Expenditures (Details) Sheet http://www.warriormetcoal.com/role/SegmentInformationReconciliationofCapitalExpendituresDetails Segment Information - Reconciliation of Capital Expenditures (Details) Details 50 false false R51.htm 2444423 - Disclosure - Segment Information - Reconciliation of Net Income (Loss) (Details) Sheet http://www.warriormetcoal.com/role/SegmentInformationReconciliationofNetIncomeLossDetails Segment Information - Reconciliation of Net Income (Loss) (Details) Details 51 false false R52.htm 2446424 - Disclosure - Subsequent Events (Details) Sheet http://www.warriormetcoal.com/role/SubsequentEventsDetails Subsequent Events (Details) Details http://www.warriormetcoal.com/role/SubsequentEvents 52 false false All Reports Book All Reports hcc-20210331.htm exhibit311-3312021.htm exhibit312-3312021.htm exhibit321-3312021.htm exhibit95-3312021.htm hcc-20210331.xsd hcc-20210331_cal.xml hcc-20210331_def.xml hcc-20210331_lab.xml hcc-20210331_pre.xml hcc-20210331_g1.jpg http://fasb.org/us-gaap/2020-01-31 http://fasb.org/srt/2020-01-31 http://xbrl.sec.gov/dei/2020-01-31 true true