1.0.0.3 false Statement Of Cash Flows Indirect (USD $) In Thousands false 1 $ false false Shares Standard http://www.xbrl.org/2003/instance shares 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDperShareItemType Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 0 false 2 $ false false Shares Standard http://www.xbrl.org/2003/instance shares 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDperShareItemType Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 0 5 Cash Flows From 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 aye_ProfitLoss aye false credit duration monetary No definition available. false false false false false false false false false 1 true true 206961000 206961 false false 2 true true 290802000 290802 false false No definition available. No authoritative reference available. false 7 Adjustments for non-cash items included in income: 4 us-gaap_AdjustmentsForNoncashItemsIncludedInIncomeLossFromContinuingOperationsAbstract 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 and amortization 5 us-gaap_DepreciationAndAmortization us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 135732000 135732 false false 2 false true 139083000 139083 false false No definition available. No authoritative reference available. false 9 Amortization of debt related costs 5 us-gaap_AmortizationOfFinancingCosts us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 5584000 5584 false false 2 false true 5439000 5439 false false No definition available. No authoritative reference available. false 10 Amortization of liability for adverse power purchase commitment 5 aye_AmortizationOfLiabilityAboveMarketForNonutilityGeneratorContracts aye false debit duration monetary No definition available. false false false false false false false false false 1 false true -8734000 -8734 false false 2 false true -8568000 -8568 false false No definition available. No authoritative reference available. false 11 Amortization of Pennsylvania stranded costs 5 us-gaap_AmortizationOfRegulatoryAsset 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 8068000 8068 false false No definition available. No authoritative reference available. false 12 Provision for uncollectible accounts 5 us-gaap_ProvisionForDoubtfulAccounts us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 7184000 7184 false false 2 false true 10475000 10475 false false No definition available. No authoritative reference available. false 13 Deferred income taxes and investment tax credit, net 5 us-gaap_DeferredIncomeTaxesAndTaxCredits us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 135833000 135833 false false 2 false true 121763000 121763 false false No definition available. No authoritative reference available. false 14 Deferred energy costs, net 5 aye_DeferredEnergyCostsNet aye false debit duration monetary No definition available. false false false false false false false false false 1 false true -24582000 -24582 false false 2 false true -9351000 -9351 false false No definition available. No authoritative reference available. false 15 Stock-based compensation expense 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 8588000 8588 false false 2 false true 6353000 6353 false false No definition available. No authoritative reference available. false 16 Unrealized gains on derivative contracts, net 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 -35622000 -35622 false false 2 false true -154603000 -154603 false false No definition available. No authoritative reference available. false 17 Pension and other postretirement employee benefit plan expense 5 us-gaap_PensionAndOtherPostretirementBenefitExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 20137000 20137 false false 2 false true 15825000 15825 false false No definition available. No authoritative reference available. false 18 Pension and other postretirement employee benefit plan contributions 5 us-gaap_PensionAndOtherPostretirementBenefitContributions us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -4187000 -4187 false false 2 false true -42039000 -42039 false false No definition available. No authoritative reference available. false 19 Deferred revenue - Fort Martin scrubber project 5 aye_DeferredRevenueForProjects aye false debit duration monetary No definition available. false false false false false false false false false 1 false true 4805000 4805 false false 2 false true 7653000 7653 false false No definition available. No authoritative reference available. false 20 Deferred revenue - Virginia 5 us-gaap_RecognitionOfDeferredRevenue us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -28333000 -28333 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 21 Uncollected transmission revenue 5 aye_UncollectedTransmissionRevenue aye false debit duration monetary No definition available. false false false false false false false false false 1 false true -7210000 -7210 false false 2 false true -10234000 -10234 false false No definition available. No authoritative reference available. false 22 Other, net 5 us-gaap_OtherAdjustmentsForNoncashItemsIncludedInIncomeLossFromContinuingOperations us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 4183000 4183 false false 2 false true 8893000 8893 false false No definition available. No authoritative reference available. false 23 Changes in certain assets and liabilities: 4 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 24 Accounts receivable, net 5 us-gaap_IncreaseDecreaseInAccountsReceivable us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -26590000 -26590 false false 2 false true -65812000 -65812 false false No definition available. No authoritative reference available. false 25 Materials, supplies and fuel 5 us-gaap_IncreaseDecreaseInInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -75215000 -75215 false false 2 false true -44918000 -44918 false false No definition available. No authoritative reference available. false 26 Prepaid taxes 5 us-gaap_IncreaseDecreaseInPrepaidExpense us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -11621000 -11621 false false 2 false true -6339000 -6339 false false No definition available. No authoritative reference available. false 27 Collateral deposits 5 us-gaap_IncreaseDecreaseInDepositsOutstanding us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -655000 -655 false false 2 false true 29082000 29082 false false No definition available. No authoritative reference available. false 28 Accounts payable 5 us-gaap_IncreaseDecreaseInAccountsPayable us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -12658000 -12658 false false 2 false true 99000 99 false false No definition available. No authoritative reference available. false 29 Accrued taxes 5 us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -66096000 -66096 false false 2 false true -11455000 -11455 false false No definition available. No authoritative reference available. false 30 Accrued interest 5 us-gaap_IncreaseDecreaseInInterestPayableNet us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -1500000 -1500 false false 2 false true -8352000 -8352 false false No definition available. No authoritative reference available. false 31 Regulatory assets 5 us-gaap_IncreaseDecreaseInOtherRegulatoryAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 32972000 32972 false false 2 false true 4618000 4618 false false No definition available. No authoritative reference available. false 32 Deferred income taxes 5 us-gaap_IncreaseDecreaseInDeferredIncomeTaxes us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -22521000 -22521 false false 2 false true -1452000 -1452 false false No definition available. No authoritative reference available. false 33 Regulatory liabilities 5 us-gaap_IncreaseDecreaseInRegulatoryLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -6032000 -6032 false false 2 false true 27890000 27890 false false No definition available. No authoritative reference available. false 34 Distributions from equity method investee 5 us-gaap_EquityMethodInvestmentDividendsOrDistributions us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1275000 1275 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 35 Assets and liabilities held for sale 5 aye_IncreaseDecreaseInNetAssetsHeldForSale aye false credit duration monetary No definition available. false false false false false false false false false 1 false true 3042000 3042 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 36 Other operating assets and liabilities 5 us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 6253000 6253 false false 2 false true 1217000 1217 false false No definition available. No authoritative reference available. false 37 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 240993000 240993 false false 2 false true 314137000 314137 false false No definition available. No authoritative reference available. true 38 Cash Flows From 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 39 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 -550230000 -550230 false false 2 false true -478391000 -478391 false false No definition available. No authoritative reference available. false 40 Proceeds from asset sales 4 us-gaap_ProceedsFromSaleOfProductiveAssets us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 200000 200 false false 2 false true 400000 400 false false No definition available. No authoritative reference available. false 41 Purchase of Merrill Lynch interest in subsidiary 4 us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries 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 -50000000 -50000 false false No definition available. No authoritative reference available. false 42 Decrease in restricted funds 4 us-gaap_IncreaseDecreaseInRestrictedCash us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 104633000 104633 false false 2 false true 58250000 58250 false false No definition available. No authoritative reference available. false 43 Other investments 4 us-gaap_PaymentsToAcquireOtherInvestments us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1442000 -1442 false false 2 false true -1474000 -1474 false false No definition available. No authoritative reference available. false 44 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 -446839000 -446839 false false 2 false true -471215000 -471215 false false No definition available. No authoritative reference available. true 45 Cash Flows From 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 46 Issuance of long-term debt 4 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 277084000 277084 false false 2 false true 249148000 249148 false false No definition available. No authoritative reference available. false 47 Repayment of 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 -167332000 -167332 false false 2 false true -196624000 -196624 false false No definition available. No authoritative reference available. false 48 Equity contribution to PATH, LLC by the joint venture partner 4 aye_ProceedsFromContributionsFromJointVenturePartner aye false debit duration monetary No definition available. false false false false false false false false false 1 false true 470000 470 false false 2 false true 4460000 4460 false false No definition available. No authoritative reference available. false 49 Distribution on behalf of noncontrolling interest 4 us-gaap_PaymentsToMinorityShareholders us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -249000 -249 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 50 Payments on capital lease obligations 4 us-gaap_RepaymentsOfLongTermCapitalLeaseObligations us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -4361000 -4361 false false 2 false true -4371000 -4371 false false No definition available. No authoritative reference available. false 51 Share-based excess tax benefits 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 19732000 19732 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 52 Proceeds from exercise of employee 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 1225000 1225 false false 2 false true 16748000 16748 false false No definition available. No authoritative reference available. false 53 Cash dividends paid on common stock 4 us-gaap_PaymentsOfDividendsCommonStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -50830000 -50830 false false 2 false true -50413000 -50413 false false No definition available. No authoritative reference available. false 54 Net cash 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 75739000 75739 false false 2 false true 18948000 18948 false false No definition available. No authoritative reference available. true 55 Net decrease 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 -130107000 -130107 false false 2 false true -138130000 -138130 false false No definition available. No authoritative reference available. true 56 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 362145000 362145 false false 2 false true 258750000 258750 false false No definition available. No authoritative reference available. false 57 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 232038000 232038 false false 2 false true 120620000 120620 false false No definition available. No authoritative reference available. false 58 Supplemental Cash Flows Information: 3 us-gaap_SupplementalCashFlowInformationAbstract 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 59 Cash paid during the period for interest (net of amounts capitalized) 4 us-gaap_InterestPaidNet us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 111984000 111984 false false 2 false true 119848000 119848 false false No definition available. No authoritative reference available. false 60 Accounts payable at June 30 relating to capital expenditures 4 aye_PropertyPlantAndEquipmentAdditionsInAccountsPayable aye false credit duration monetary No definition available. false false false false false false false false false 1 true true 96676000 96676 false false 2 true true 73204000 73204 false false No definition available. No authoritative reference available. false false 2 56 false Thousands UnKnown UnKnown false true