1.0.0.3 false Condensed Consolidated Statements of Cash Flows (USD $) In Thousands false 1 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u002 Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u002 Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 5 Operating activities 3 us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 6 Net income 4 us-gaap_NetIncomeLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 36824000 36824 false false 2 true true 160093000 160093 false false No definition available. No authoritative reference available. false 7 Adjustments to reconcile net income to net cash provided by operating activities 4 us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 8 Depreciation, depletion and amortization 5 us-gaap_DepreciationDepletionAndAmortization us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 156020000 156020 false false 2 false true 131366000 131366 false false No definition available. No authoritative reference available. false 9 Amortization of acquired coal supply agreements, net 5 us-gaap_AmortizationOfIntangibleAssets us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 57983000 57983 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 10 Amortization of debt issuance costs 5 anr_AmortizationOfDebtIssuanceCosts anr false na duration monetary Amortization of Debt Issuance Costs false false false false false false false false false 1 false true 2588000 2588 false false 2 false true 2985000 2985 false false Amortization of Debt Issuance Costs No authoritative reference available. false 11 Discontinuance of cash flow hedge on interest rate swap 5 us-gaap_LossOnCashFlowHedgeIneffectiveness us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 23549000 23549 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 12 Accretion of asset retirement obligation 5 us-gaap_AssetRetirementObligationAccretionExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 7717000 7717 false false 2 false true 5553000 5553 false false No definition available. No authoritative reference available. false 13 Accretion of debt discount 5 anr_AccretionOfDebtDiscount anr false na duration monetary Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values.... false false false false false false false false false 1 false true 8327000 8327 false false 2 false true 5110000 5110 false false Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations. Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations. No authoritative reference available. false 14 Loss on early extinguishment of debt 5 us-gaap_GainsLossesOnExtinguishmentOfDebt us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 5641000 5641 false false 2 false true 14702000 14702 false false No definition available. No authoritative reference available. false 15 Share-based compensation 5 us-gaap_ShareBasedCompensation us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 26650000 26650 false false 2 false true 15873000 15873 false false No definition available. No authoritative reference available. false 16 Gain on sale of discontinued operations 5 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -13635000 -13635 false false No definition available. No authoritative reference available. false 17 Gain on sale of coal reserves 5 anr_GainOnSaleOfCoalReserves anr false na duration monetary The difference between the book value and the sale price of property that has been found to have proven coal reserves. This... false false false false false false false false false 1 false true 0 0 false false 2 false true -11446000 -11446 false false The difference between the book value and the sale price of property that has been found to have proven coal reserves. This element refers to the gain (loss). No authoritative reference available. false 18 Unrealized mark-to-market (gains) losses on derivative instruments 5 us-gaap_UnrealizedGainLossOnDerivatives us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -18270000 -18270 false false 2 false true 11094000 11094 false false No definition available. No authoritative reference available. false 19 Deferred income taxes 5 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -48890000 -48890 false false 2 false true -1158000 -1158 false false No definition available. No authoritative reference available. false 20 Other, net 5 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesOther us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1069000 1069 false false 2 false true -3235000 -3235 false false No definition available. No authoritative reference available. false 21 Changes in operating assets and liabilities 5 us-gaap_IncreaseDecreaseInOperatingCapitalAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 22 Trade accounts receivable, net 6 us-gaap_IncreaseDecreaseInAccountsReceivable us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -18643000 -18643 false false 2 false true -47659000 -47659 false false No definition available. No authoritative reference available. false 23 Inventories, net 6 us-gaap_IncreaseDecreaseInInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -23454000 -23454 false false 2 false true -13265000 -13265 false false No definition available. No authoritative reference available. false 24 Prepaid expenses and other current assets 6 anr_PrepaidExpensesAndOtherCurrentAssets anr false credit duration monetary Prepaid Expenses and Other Current Assets false false false false false false false false false 1 false true -21565000 -21565 false false 2 false true 16111000 16111 false false Prepaid Expenses and Other Current Assets No authoritative reference available. false 25 Other non-current assets 6 us-gaap_IncreaseDecreaseInOtherOperatingAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 1297000 1297 false false 2 false true 1332000 1332 false false No definition available. No authoritative reference available. false 26 Trade accounts payable 6 us-gaap_IncreaseDecreaseInAccountsPayable us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -18875000 -18875 false false 2 false true 39998000 39998 false false No definition available. No authoritative reference available. false 27 Accrued expenses and other current liabilities 6 anr_IncreaseDecreaseAccruedExpenseAndOtherCurrentLiabilities anr false na duration monetary Accrued expenses and other current liabilities false false false false false false false false false 1 false true -10477000 -10477 false false 2 false true 20198000 20198 false false Accrued expenses and other current liabilities No authoritative reference available. false 28 Pension and postretirement medical benefit obligations 6 us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -10552000 -10552 false false 2 false true 6627000 6627 false false No definition available. No authoritative reference available. false 29 Asset retirement obligations 6 us-gaap_IncreaseDecreaseInAssetRetirementObligations us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -4676000 -4676 false false 2 false true -3891000 -3891 false false No definition available. No authoritative reference available. false 30 Other non-current liabilities 6 us-gaap_IncreaseDecreaseInOtherOperatingLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 9853000 9853 false false 2 false true -950000 -950 false false No definition available. No authoritative reference available. false 31 Net cash provided by operating activities 4 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 162116000 162116 false false 2 false true 335803000 335803 false false No definition available. No authoritative reference available. true 32 Investing activities 3 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 33 Capital expenditures 4 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -102816000 -102816 false false 2 false true -113632000 -113632 false false No definition available. No authoritative reference available. false 34 Cash acquired from a merger 4 us-gaap_CashAcquiredFromAcquisition us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 23505000 23505 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 35 Proceeds from disposition of property and equipment 4 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 522000 522 false false 2 false true 16241000 16241 false false No definition available. No authoritative reference available. false 36 Proceeds from sale of investment in coal terminal 4 us-gaap_ProceedsFromSaleMaturityAndCollectionsOfInvestments us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 1500000 1500 false false No definition available. No authoritative reference available. false 37 Proceeds from sale of discontinued operations 4 us-gaap_ProceedsFromDivestitureOfBusinesses us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 45000000 45000 false false No definition available. No authoritative reference available. false 38 Other, net 4 us-gaap_PaymentsForProceedsFromOtherInvestingActivities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1615000 -1615 false false 2 false true -3247000 -3247 false false No definition available. No authoritative reference available. false 39 Net cash used in investing activities 4 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -80404000 -80404 false false 2 false true -54138000 -54138 false false No definition available. No authoritative reference available. true 40 Financing activities 3 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 41 Proceeds from issuance of convertible debt 4 us-gaap_ProceedsFromConvertibleDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 287500000 287500 false false No definition available. No authoritative reference available. false 42 Principal repayments of note payable 4 us-gaap_RepaymentsOfNotesPayable us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -16429000 -16429 false false 2 false true -18883000 -18883 false false No definition available. No authoritative reference available. false 43 Principal repayments on long-term debt 4 us-gaap_RepaymentsOfLongTermDebt us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -241500000 -241500 false false 2 false true -193921000 -193921 false false No definition available. No authoritative reference available. false 44 Debt issuance costs 4 us-gaap_PaymentsOfDebtIssuanceCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -11218000 -11218 false false 2 false true -10861000 -10861 false false No definition available. No authoritative reference available. false 45 Premium payment on early extinguishment of debt 4 us-gaap_PaymentsOfDebtRestructuringCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -10736000 -10736 false false No definition available. No authoritative reference available. false 46 Excess tax benefit from share-based awards 4 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 3143000 3143 false false No definition available. No authoritative reference available. false 47 Proceeds from issuance of common stock, net 4 us-gaap_ProceedsFromIssuanceOfCommonStock us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 164666000 164666 false false No definition available. No authoritative reference available. false 48 Common stock repurchases 4 us-gaap_PaymentsForRepurchaseOfCommonStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -8495000 -8495 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 49 Proceeds from exercise of stock options 4 us-gaap_ProceedsFromStockOptionsExercised us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 2419000 2419 false false 2 false true 3356000 3356 false false No definition available. No authoritative reference available. false 50 Other, net 4 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -1122000 -1122 false false 2 false true -160000 -160 false false No definition available. No authoritative reference available. false 51 Net cash (used in) provided by financing activities 4 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -276345000 -276345 false false 2 false true 224104000 224104 false false No definition available. No authoritative reference available. true 52 Net (decrease) increase in cash and cash equivalents 3 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true -194633000 -194633 false false 2 false true 505769000 505769 false false No definition available. No authoritative reference available. true 53 Cash and cash equivalents at beginning of period 3 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false true false false 1 false true 676190000 676190 false false 2 false true 54365000 54365 false false No definition available. No authoritative reference available. false 54 Cash and cash equivalents at end of period 3 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false true false 1 false true 481557000 481557 false false 2 false true 560134000 560134 false false No definition available. No authoritative reference available. false 55 Issuance of common stock for acquisition accounting 3 us-gaap_StockIssued us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 true true 1628601000 1628601 false false 2 true true 0 0 false false No definition available. No authoritative reference available. false false 2 51 false Thousands UnKnown UnKnown false true