1.0.0.3 false Statement Of Shareholders Equity And Other Comprehensive Income (Parenthetical) (USD $) In Millions false 1 $ false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 iso4217_USD_per_shares Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 0 shares Standard http://www.xbrl.org/2003/instance shares 0 false 2 $ false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 iso4217_USD_per_shares Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 0 shares Standard http://www.xbrl.org/2003/instance shares 0 false 3 $ false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 iso4217_USD_per_shares Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 0 shares Standard http://www.xbrl.org/2003/instance shares 0 5 Net gain (loss) during the period, tax 3 us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansTax us-gaap true na duration monetary No definition available. false false false false false false false false false 1 true true 3100000 3.1 false false 2 true true 26900000 26.9 false false 3 true true 10600000 10.6 false false No definition available. No authoritative reference available. false 6 Amortization, tax 3 us-gaap_OtherComprehensiveIncomeAmortizationOfDefinedBenefitPlanNetPriorServiceCostRecognizedInNetPeriodicPensionCostTax us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 2100000 2.1 false false 2 false true 1100000 1.1 false false 3 false true 2400000 2.4 false false No definition available. No authoritative reference available. false 7 Cash flow hedges, tax 3 us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesTaxEffectPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 28500000 28.5 false false 2 false true 20500000 20.5 false false 3 false true 2900000 2.9 false false No definition available. No authoritative reference available. false 8 Service cost, interest cost and expected return on plan assets, tax 3 aye_TaxOnServiceCostInterestCostAndExpectedReturnOnPlanAssets aye false credit duration monetary Tax On Service Cost, Interest Cost And Expected Return On Plan Assets false false false false false false false false false 1 false false 0 0 false false 2 false true 3000000 3.0 false false 3 false false 0 0 false false Tax On Service Cost, Interest Cost And Expected Return On Plan Assets No authoritative reference available. false 9 Establishment of regulatory asset related to pension obligation, tax 3 aye_TaxOnEstablishmentOfRegulatoryAssetsRelatedToPensionObligation aye false debit duration monetary Tax On Establishment Of Regulatory Assets Related To Pension Obligation false false false false false false false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false true 35700000 35.7 false false Tax On Establishment Of Regulatory Assets Related To Pension Obligation No authoritative reference available. false 10 Net actuarial loss, tax 3 aye_TaxOnAmortizationNetActuarialLoss aye false credit duration monetary Tax On Amortization Net Actuarial Loss false false false false false false false false false 1 false false 0 0 false false 2 false true 700000 0.7 false false 3 false false 0 0 false false Tax On Amortization Net Actuarial Loss No authoritative reference available. false 11 Adjustment related to 2005 SO2 allowance sale, tax 3 aye_TaxOnAdjustmentRelatedToAllowanceSO2AllowanceSale aye false debit duration monetary Tax On Adjustment Related To Allowance SO2 AllowanceS ale false false false false false false false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false true 5800000 5.8 false false Tax On Adjustment Related To Allowance SO2 AllowanceS ale No authoritative reference available. false 12 Net transition obligation, tax 3 aye_TaxOnAmortizationNetTransitionObligation aye false credit duration monetary Tax On Amortization Net Transition Obligation false false false false false false false false false 1 false false 0 0 false false 2 false true 600000 0.6 false false 3 false false 0 0 false false Tax On Amortization Net Transition Obligation No authoritative reference available. false 13 Net prior service cost, tax 3 aye_TaxOnAmortizationNetPriorServiceCosts aye false credit duration monetary Tax On Amortization Net Prior Service Costs false false false false false false false false false 1 false false 0 0 false false 2 true true 300000 0.3 false false 3 false false 0 0 false false Tax On Amortization Net Prior Service Costs No authoritative reference available. false false 3 9 false HundredThousands UnKnown UnKnown false true