1.0.0.3 false CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Millions false 1 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 false 2 $ false false u000 Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 u001 Standard http://www.xbrl.org/2003/instance shares xbrli 0 6 Current Assets 4 us-gaap_AssetsCurrentAbstract 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 7 Cash and cash equivalents 5 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false false 0 0 false false 2 true true 23900000 23.9 false false No definition available. No authoritative reference available. false 8 Accounts receivable, net 5 us-gaap_AccountsReceivableNetCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 221100000 221.1 false false 2 false true 386600000 386.6 false false No definition available. No authoritative reference available. false 9 Unbilled-gas accounts receivable 5 us-gaap_UnbilledContractsReceivable us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 19500000 19.5 false false 2 false true 95800000 95.8 false false No definition available. No authoritative reference available. false 10 Fair value of derivative contracts 5 us-gaap_DerivativeAssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 184900000 184.9 false false 2 false true 431300000 431.3 false false No definition available. No authoritative reference available. false 11 Gas and oil storage 5 us-gaap_EnergyRelatedInventoryGasStoredUnderground us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 66200000 66.2 false false 2 false true 85500000 85.5 false false No definition available. No authoritative reference available. false 12 Materials and supplies 5 us-gaap_OtherInventorySupplies us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 112800000 112.8 false false 2 false true 106900000 106.9 false false No definition available. No authoritative reference available. false 13 Prepaid expenses and other 5 us-gaap_PrepaidExpenseCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 86900000 86.9 false false 2 false true 55000000 55.0 false false No definition available. No authoritative reference available. false 14 Total Current Assets 5 us-gaap_AssetsCurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 691400000 691.4 false false 2 false true 1185000000 1185.0 false false No definition available. No authoritative reference available. true 15 Property, Plant and Equipment (successful efforts method for gas and oil properties) 4 us-gaap_PropertyPlantAndEquipmentGross us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 11049600000 11049.6 false false 2 false true 10229800000 10229.8 false false No definition available. No authoritative reference available. false 16 Accumulated depreciation, depletion and amortization 4 us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true -3579200000 -3579.2 false false 2 false true -3096800000 -3096.8 false false No definition available. No authoritative reference available. false 17 Net Property, Plant and Equipment 4 us-gaap_PropertyPlantAndEquipmentNet us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 7470400000 7470.4 false false 2 false true 7133000000 7133.0 false false No definition available. No authoritative reference available. true 18 Investment in unconsolidated affiliates 4 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 71400000 71.4 false false 2 false true 68400000 68.4 false false No definition available. No authoritative reference available. false 19 Goodwill 4 us-gaap_Goodwill us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 69900000 69.9 false false 2 false true 70000000 70.0 false false No definition available. No authoritative reference available. false 20 Regulatory assets 4 us-gaap_RegulatoryAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 24300000 24.3 false false 2 false true 26300000 26.3 false false No definition available. No authoritative reference available. false 21 Fair value of derivative contracts 4 us-gaap_DerivativeAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 11400000 11.4 false false 2 false true 106300000 106.3 false false No definition available. No authoritative reference available. false 22 Other noncurrent assets, net 4 us-gaap_OtherAssetsNoncurrent us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 41700000 41.7 false false 2 false true 41700000 41.7 false false No definition available. No authoritative reference available. false 23 Total Assets 4 us-gaap_Assets us-gaap true debit instant monetary No definition available. false false false false false false false false false 1 false true 8380500000 8380.5 false false 2 false true 8630700000 8630.7 false false No definition available. No authoritative reference available. true 25 Current Liabilities 4 us-gaap_LiabilitiesCurrentAbstract 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 26 Checks outstanding in excess of cash balances 5 us-gaap_BankOverdrafts us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 14100000 14.1 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 27 Short-term debt 5 us-gaap_ShortTermBorrowings us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 38500000 38.5 false false 2 false true 231100000 231.1 false false No definition available. No authoritative reference available. false 28 Accounts payable and accrued expenses 5 us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 449900000 449.9 false false 2 false true 682900000 682.9 false false No definition available. No authoritative reference available. false 29 Fair value of derivative contracts 5 us-gaap_DerivativeLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 109300000 109.3 false false 2 false true 500000 0.5 false false No definition available. No authoritative reference available. false 30 Purchase-gas adjustment 5 us-gaap_DeferredGasPurchasesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 37100000 37.1 false false 2 false true 45800000 45.8 false false No definition available. No authoritative reference available. false 31 Deferred income taxes - current 5 us-gaap_DeferredTaxLiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 35500000 35.5 false false 2 false true 130600000 130.6 false false No definition available. No authoritative reference available. false 32 Current portion of long-term debt 5 us-gaap_LongTermDebtCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 42000000 42.0 false false 2 false true 42000000 42.0 false false No definition available. No authoritative reference available. false 33 Total Current Liabilities 5 us-gaap_LiabilitiesCurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 726400000 726.4 false false 2 false true 1132900000 1132.9 false false No definition available. No authoritative reference available. true 34 Long-term debt, less current portion 4 us-gaap_LongTermDebtNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 2104900000 2104.9 false false 2 false true 2078900000 2078.9 false false No definition available. No authoritative reference available. false 35 Deferred income taxes 4 us-gaap_DeferredTaxLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 1399100000 1399.1 false false 2 false true 1334100000 1334.1 false false No definition available. No authoritative reference available. false 36 Asset retirement obligations 4 us-gaap_AssetRetirementObligationsNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 186100000 186.1 false false 2 false true 175600000 175.6 false false No definition available. No authoritative reference available. false 37 Pension and postretirement benefits 4 us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 253200000 253.2 false false 2 false true 250000000 250.0 false false No definition available. No authoritative reference available. false 38 Fair value of derivative contracts 4 us-gaap_DerivativeLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 185000000 185.0 false false 2 false true 69000000 69.0 false false No definition available. No authoritative reference available. false 39 Other long-term liabilities 4 us-gaap_OtherLiabilitiesNoncurrent us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 129000000 129.0 false false 2 false true 142700000 142.7 false false No definition available. No authoritative reference available. false 40 EQUITY 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract 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 Common stock 5 us-gaap_CommonStockValue us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 443300000 443.3 false false 2 false true 451000000 451.0 false false No definition available. No authoritative reference available. false 42 Retained earnings 5 us-gaap_RetainedEarningsAccumulatedDeficit us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 2950300000 2950.3 false false 2 false true 2772300000 2772.3 false false No definition available. No authoritative reference available. false 43 Accumulated other comprehensive income (loss) 5 us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true -51900000 -51.9 false false 2 false true 194700000 194.7 false false No definition available. No authoritative reference available. false 44 Total Common Shareholders' Equity 5 us-gaap_StockholdersEquity us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 3341700000 3341.7 false false 2 false true 3418000000 3418.0 false false No definition available. No authoritative reference available. true 45 Noncontrolling interest 5 us-gaap_MinorityInterest us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 55100000 55.1 false false 2 false true 29500000 29.5 false false No definition available. No authoritative reference available. false 46 Total Equity 5 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 false true 3396800000 3396.8 false false 2 false true 3447500000 3447.5 false false No definition available. No authoritative reference available. true 47 Total Liabilities and Equity 4 us-gaap_LiabilitiesAndStockholdersEquity us-gaap true credit instant monetary No definition available. false false false false false false false false false 1 true true 8380500000 8380.5 false false 2 true true 8630700000 8630.7 false false No definition available. No authoritative reference available. true false 2 41 false HundredThousands UnKnown UnKnown false true