$ATO
Atmos Energy Corp Stock $ato

$ato Overview Financials Valuation SEC Filings Company Website

2017 Q3 Form 10-K Financial Statement

#000073180217000041 Filed on November 13, 2017

Income Statement

Concept	2017 Q3	2016 Q3	2016 Q2
Revenue	$464.9M	$433.6M	$456.2M
YoY Change	7.2%	5.47%	0.16%
Cost Of Revenue	$72.60M	$63.90M	$64.60M
YoY Change	13.62%	-78.88%	-78.8%
Gross Profit	$392.3M	$369.7M	$391.6M
YoY Change	6.11%	7.39%	6.38%
Gross Profit Margin	84.39%	85.26%	85.84%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$84.80M	$76.40M	$73.50M
YoY Change	10.99%	8.06%	7.3%
% of Gross Profit	21.62%	20.66%	18.77%
Operating Expenses	$300.5M	$285.3M	$270.1M
YoY Change	5.33%	2.48%	2.3%
Operating Profit	$91.79M	$84.45M	$128.4M
YoY Change	8.7%	13.59%	15.67%
Interest Expense	-$33.70M	-$30.00M	$27.68M
YoY Change	12.33%	-3.54%	-0.99%
% of Operating Profit	-36.71%	-35.52%	21.56%
Other Income/Expense, Net	-$2.800M	-$100.0K	$1.118M
YoY Change	2700.0%	-94.44%	76.34%
Pretax Income	$55.30M	$54.30M	$101.8M
YoY Change	1.84%	26.28%	12.79%
Income Tax	$19.40M	$19.40M	$35.69M
% Of Pretax Income	35.08%	35.73%	35.05%
Net Earnings	$35.85M	$34.24M	$71.19M
YoY Change	4.71%	45.61%	26.5%
Net Earnings / Revenue	7.71%	7.9%	15.61%
Basic Earnings Per Share		$0.33	$0.69
Diluted Earnings Per Share	$336.1K	$0.33	$0.69
COMMON SHARES
Basic Shares Outstanding	106.1M shares	103.8M shares	102.2M shares
Diluted Shares Outstanding

Balance Sheet

Concept	2017 Q3	2016 Q3	2016 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$114.8M	$120.2M	$66.00M
YoY Change	-4.51%	16.9%	53.49%
Cash & Equivalents	$26.41M	$47.53M	$66.21M
Short-Term Investments	$88.41M	$72.70M
Other Short-Term Assets	$106.3M	$88.09M	$60.50M
YoY Change	20.7%	76.42%	3.25%
Inventory	$185.0M	$179.0M	$245.0M
Prepaid Expenses	$32.16M	$21.49M
Receivables	$222.3M	$215.9M	$277.4M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$539.6M	$681.7M	$648.9M
YoY Change	-20.84%	8.84%	5.23%
LONG-TERM ASSETS
Property, Plant & Equipment	$9.259B	$8.269B	$8.054B
YoY Change	11.97%	11.28%	11.67%
Goodwill	$730.1M	$727.0M	$742.7M
YoY Change	0.44%	0.1%	0.09%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$220.6M	$305.0M	$282.2M
YoY Change	-27.66%	10.75%	-10.05%
Total Long-Term Assets	$10.21B	$9.329B	$9.078B
YoY Change	9.44%	10.42%	9.8%
TOTAL ASSETS
Total Short-Term Assets	$539.6M	$681.7M	$648.9M
Total Long-Term Assets	$10.21B	$9.329B	$9.078B
Total Assets	$10.75B	$10.01B	$9.727B
YoY Change	7.38%	10.31%	9.49%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$233.0M	$196.0M	$199.0M
YoY Change	18.88%	-17.99%	-12.33%
Accrued Expenses
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$447.7M	$829.8M	$670.5M
YoY Change	-46.04%	81.21%	166.08%
Long-Term Debt Due	$0.00	$250.0M	$250.0M
YoY Change	-100.0%
Total Short-Term Liabilities	$1.013B	$1.788B	$1.530B
YoY Change	-43.33%	54.85%	66.9%
LONG-TERM LIABILITIES
Long-Term Debt	$3.067B	$2.189B	$2.206B
YoY Change	40.13%	-10.2%	-10.17%
Other Long-Term Liabilities	$175.7M	$245.4M	$228.8M
YoY Change	-28.38%	52.08%	140.9%
Total Long-Term Liabilities	$3.243B	$2.434B	$2.434B
YoY Change	33.22%	-6.34%	-4.54%
TOTAL LIABILITIES
Total Short-Term Liabilities	$1.013B	$1.788B	$1.530B
Total Long-Term Liabilities	$3.243B	$2.434B	$2.434B
Total Liabilities	$4.256B	$4.222B	$3.964B
YoY Change	0.8%	12.49%	14.35%
SHAREHOLDERS EQUITY
Retained Earnings	$1.467B	$1.263B	$1.273B
YoY Change	16.2%	17.66%	16.49%
Common Stock	$2.537B	$2.389B	$2.372B
YoY Change	6.21%	7.06%	7.44%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$3.899B	$3.463B	$3.467B
YoY Change
Total Liabilities & Shareholders Equity	$10.75B	$10.01B	$9.727B
YoY Change	7.38%	10.31%	9.49%

Cashflow Statement

Concept	2017 Q3	2016 Q3	2016 Q2
OPERATING ACTIVITIES
Net Income	$35.85M	$34.24M	$71.19M
YoY Change	4.71%	45.61%	26.5%
Depreciation, Depletion And Amortization	$84.80M	$76.40M	$73.50M
YoY Change	10.99%	8.06%	7.3%
Cash From Operating Activities	$121.5M	$165.1M	$176.9M
YoY Change	-26.41%	75.08%	0.06%
INVESTING ACTIVITIES
Capital Expenditures	-$325.0M	-$297.3M	-$253.7M
YoY Change	9.32%	0.41%	12.31%
Acquisitions
YoY Change
Other Investing Activities	$16.00M	$900.0K	$3.800M
YoY Change	1677.78%	-88.89%	1800.0%
Cash From Investing Activities	-$308.9M	-$296.3M	-$249.9M
YoY Change	4.25%	2.88%	10.77%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	144.1M	112.6M	91.20M
YoY Change	27.98%	-37.17%	-2705.71%
NET CHANGE
Cash From Operating Activities	121.5M	165.1M	176.9M
Cash From Investing Activities	-308.9M	-296.3M	-249.9M
Cash From Financing Activities	144.1M	112.6M	91.20M
Net Change In Cash	-43.30M	-18.60M	18.20M
YoY Change	132.8%	28.28%	-134.8%
FREE CASH FLOW
Cash From Operating Activities	$121.5M	$165.1M	$176.9M
Capital Expenditures	-$325.0M	-$297.3M	-$253.7M
Free Cash Flow	$446.5M	$462.4M	$430.6M
YoY Change	-3.44%	18.44%	6.93%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2017	ato	Atm Equity Distribution Gross Proceeds ATMEquityDistributionGrossProceeds	100000000	USD
CY2016	ato	Atm Equity Distribution Net Proceeds ATMEquityDistributionNetProceeds	98600000	USD
CY2017	ato	Atm Equity Distribution Net Proceeds ATMEquityDistributionNetProceeds	98800000	USD
CY2016Q3	ato	Atm Equity Distribution Offering Price Maximum Amount ATMEquityDistributionOfferingPriceMaximumAmount	200000000	USD
CY2016	ato	Atm Equity Distribution Shares Issued ATMEquityDistributionSharesIssued	1360756	shares
CY2017	ato	Atm Equity Distribution Shares Issued ATMEquityDistributionSharesIssued	1303494	shares
CY2016Q3	ato	Accrued Gas Payable AccruedGasPayable	47107000	USD
CY2016	ato	Atm Equity Distribution Gross Proceeds ATMEquityDistributionGrossProceeds	100000000	USD
CY2017Q3	ato	Accrued Gas Payable AccruedGasPayable	50253000	USD
CY2017Q3	ato	Annual Maximum Investment For Direct Stock Purchase Plan AnnualMaximumInvestmentForDirectStockPurchasePlan	100000	USD
CY2016Q3	ato	Asset Retirement Costs In Property Plant And Equipment AssetRetirementCostsInPropertyPlantAndEquipment	8100000	USD
CY2017Q3	ato	Asset Retirement Costs In Property Plant And Equipment AssetRetirementCostsInPropertyPlantAndEquipment	7800000	USD
CY2016Q3	ato	Available For Sale Securities Supplemental Executive Benefit Plans AvailableForSaleSecuritiesSupplementalExecutiveBenefitPlans	41300000	USD
CY2017Q3	ato	Available For Sale Securities Supplemental Executive Benefit Plans AvailableForSaleSecuritiesSupplementalExecutiveBenefitPlans	42900000	USD
CY2015	ato	Cash Flow Hedge Gain Loss Impacton Earnings CashFlowHedgeGainLossImpactonEarnings	-42894000	USD
CY2016	ato	Cash Flow Hedge Gain Loss Impacton Earnings CashFlowHedgeGainLossImpactonEarnings	-53216000	USD
CY2017	ato	Cash Flow Hedge Gain Loss Impacton Earnings CashFlowHedgeGainLossImpactonEarnings	7035000	USD
CY2015	ato	Cash Flow Hedge Gain Loss Included In Cost Of Sales Net CashFlowHedgeGainLossIncludedInCostOfSalesNet	-42041000	USD
CY2016	ato	Cash Flow Hedge Gain Loss Included In Cost Of Sales Net CashFlowHedgeGainLossIncludedInCostOfSalesNet	-52670000	USD
CY2017	ato	Cash Flow Hedge Gain Loss Included In Cost Of Sales Net CashFlowHedgeGainLossIncludedInCostOfSalesNet	8078000	USD
CY2015	ato	Cash Flow Hedge Gain Loss Reclassifiedto Purchased Gas Cost Net CashFlowHedgeGainLossReclassifiedtoPurchasedGasCostNet	-41716000	USD
CY2016	ato	Cash Flow Hedge Gain Loss Reclassifiedto Purchased Gas Cost Net CashFlowHedgeGainLossReclassifiedtoPurchasedGasCostNet	-52651000	USD
CY2017	ato	Cash Flow Hedge Gain Loss Reclassifiedto Purchased Gas Cost Net CashFlowHedgeGainLossReclassifiedtoPurchasedGasCostNet	-2612000	USD
CY2017	ato	Charitable Contribution Carryforwards Expiration Date Maximum CharitableContributionCarryforwardsExpirationDateMaximum	2022-12-31
CY2017	ato	Charitable Contribution Carryforwards Expiration Date Minimum CharitableContributionCarryforwardsExpirationDateMinimum	2018-12-31
CY2016Q3	ato	Commercial Paper Weighted Average Interest Rate CommercialPaperWeightedAverageInterestRate	0.0081
CY2017Q3	ato	Commercial Paper Weighted Average Interest Rate CommercialPaperWeightedAverageInterestRate	0.0125
CY2017Q3	ato	Debt And Equity Securities Authorized For Issuance DebtAndEquitySecuritiesAuthorizedForIssuance	2500000000.0	USD
CY2017Q3	ato	Debt And Equity Securities Available For Issuance DebtAndEquitySecuritiesAvailableForIssuance	1600000000	USD
CY2016Q3	ato	Deferred Tax Assets Charitable Contributionand Other Tax Credit Carryforwards DeferredTaxAssetsCharitableContributionandOtherTaxCreditCarryforwards	22273000	USD
CY2017Q3	ato	Deferred Tax Assets Charitable Contributionand Other Tax Credit Carryforwards DeferredTaxAssetsCharitableContributionandOtherTaxCreditCarryforwards	18873000	USD
CY2016Q3	ato	Deferred Tax Assets Deferred Credits DeferredTaxAssetsDeferredCredits	861000	USD
CY2017Q3	ato	Deferred Tax Assets Deferred Credits DeferredTaxAssetsDeferredCredits	985000	USD
CY2016Q3	ato	Deferred Tax Liabilities Pension Liability DeferredTaxLiabilitiesPensionLiability	30652000	USD
CY2017Q3	ato	Deferred Tax Liabilities Pension Liability DeferredTaxLiabilitiesPensionLiability	13101000	USD
CY2016Q3	ato	Derivative Asset Contract Netting DerivativeAssetContractNetting	39290000	USD
CY2017Q3	ato	Derivative Asset Contract Netting DerivativeAssetContractNetting	0	USD
CY2016Q3	ato	Derivative Asset Netof Contract Netting DerivativeAssetNetofContractNetting	4851000	USD
CY2017Q3	ato	Derivative Asset Netof Contract Netting DerivativeAssetNetofContractNetting	3239000	USD
CY2016Q3	ato	Derivative Cash Collateral DerivativeCashCollateral	50400000	USD
CY2016Q3	ato	Derivative Liability Contract Netting DerivativeLiabilityContractNetting	39290000	USD
CY2017Q3	ato	Derivative Liability Contract Netting DerivativeLiabilityContractNetting	0	USD
CY2016Q3	ato	Derivative Liability Netof Contract Netting DerivativeLiabilityNetofContractNetting	284394000	USD
CY2017Q3	ato	Derivative Liability Netof Contract Netting DerivativeLiabilityNetofContractNetting	112398000	USD
CY2015	ato	Fair Value Hedge Basis Ineffectiveness FairValueHedgeBasisIneffectiveness	-811000	USD
CY2016	ato	Fair Value Hedge Basis Ineffectiveness FairValueHedgeBasisIneffectiveness	1390000	USD
CY2017	ato	Fair Value Hedge Basis Ineffectiveness FairValueHedgeBasisIneffectiveness	597000	USD
CY2015	ato	Fair Value Hedge Timing Ineffectiveness FairValueHedgeTimingIneffectiveness	268000	USD
CY2016	ato	Fair Value Hedge Timing Ineffectiveness FairValueHedgeTimingIneffectiveness	-22985000	USD
CY2017	ato	Fair Value Hedge Timing Ineffectiveness FairValueHedgeTimingIneffectiveness	-3888000	USD
CY2015	ato	Gain Loss On Hedge Ineffectiveness GainLossOnHedgeIneffectiveness	200000	USD
CY2016	ato	Gain Loss On Hedge Ineffectiveness GainLossOnHedgeIneffectiveness	21600000	USD
CY2017	ato	Gain Loss On Hedge Ineffectiveness GainLossOnHedgeIneffectiveness	3400000	USD
CY2017	ato	Hedge Percentage Of Actual Heating Season Gas HedgePercentageOfActualHeatingSeasonGas	0.27
CY2017	ato	Hedge Volume Of Actual Heating Season Gas HedgeVolumeOfActualHeatingSeasonGas	16200	MMcf
CY2016Q3	ato	Hedged Portion Of Gas Stored Underground Fair Value Disclosure HedgedPortionOfGasStoredUndergroundFairValueDisclosure	52578000	USD
CY2015	ato	Incomefromcontinuingoperationsavailabletocommonshareholders Incomefromcontinuingoperationsavailabletocommonshareholders	305016000	USD
CY2016	ato	Incomefromcontinuingoperationsavailabletocommonshareholders Incomefromcontinuingoperationsavailabletocommonshareholders	345004000	USD
CY2017	ato	Incomefromcontinuingoperationsavailabletocommonshareholders Incomefromcontinuingoperationsavailabletocommonshareholders	382236000	USD
CY2015	ato	Incomefromdiscontinuedoperationsnetoftaxbeforegainondisposal Incomefromdiscontinuedoperationsnetoftaxbeforegainondisposal	9452000	USD
CY2016	ato	Incomefromdiscontinuedoperationsnetoftaxbeforegainondisposal Incomefromdiscontinuedoperationsnetoftaxbeforegainondisposal	4562000	USD
CY2017	ato	Incomefromdiscontinuedoperationsnetoftaxbeforegainondisposal Incomefromdiscontinuedoperationsnetoftaxbeforegainondisposal	10994000	USD
CY2015	ato	Investment Tax Credits InvestmentTaxCredits	6000	USD
CY2016	ato	Investment Tax Credits InvestmentTaxCredits	5000	USD
CY2017	ato	Investment Tax Credits InvestmentTaxCredits	0	USD
CY2017Q3	ato	Lossonsettlementofinterestrateswaps Lossonsettlementofinterestrateswaps	37000000	USD
CY2017	ato	Maximum Hedge Percentage Of Anticipated Heating Season Gas MaximumHedgePercentageOfAnticipatedHeatingSeasonGas	0.50
CY2017Q3	ato	Minimum Continuing Investment For Direct Stock Purchase Plan MinimumContinuingInvestmentForDirectStockPurchasePlan	25	USD
CY2017	ato	Minimum Hedge Percentage Of Anticipated Heating Season Gas MinimumHedgePercentageOfAnticipatedHeatingSeasonGas	0.25
CY2017Q3	ato	Minimum Initial Investment For Direct Stock Purchase Plan MinimumInitialInvestmentForDirectStockPurchasePlan	1250	USD
CY2017	ato	Net Proceeds From Issuance Of Debt NetProceedsFromIssuanceOfDebt	753000000	USD
CY2016	ato	Nonregulated Segment Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate NonregulatedSegmentEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.39
CY2017Q3	ato	Number Of Customers Regulated Distribution NumberOfCustomersRegulatedDistribution	3000000	customers
CY2017Q3	ato	Number Of Divisions Regulated Distribution NumberOfDivisionsRegulatedDistribution	6	regulated_gas_distributions_divisions
CY2016	ato	Other Comprehensive Income Reclassification Adjustment On Forward Commodity Contracts Included In Net Income Net Of Tax OtherComprehensiveIncomeReclassificationAdjustmentOnForwardCommodityContractsIncludedInNetIncomeNetOfTax	32117000	USD
CY2017	ato	Other Comprehensive Income Reclassification Adjustment On Forward Commodity Contracts Included In Net Income Net Of Tax OtherComprehensiveIncomeReclassificationAdjustmentOnForwardCommodityContractsIncludedInNetIncomeNetOfTax	-4865000	USD
CY2016	ato	Other Comprehensive Income Reclassification Adjustment On Interest Rate Agreements Included In Net Income Net Of Tax OtherComprehensiveIncomeReclassificationAdjustmentOnInterestRateAgreementsIncludedInNetIncomeNetOfTax	347000	USD
CY2017	ato	Other Comprehensive Income Reclassification Adjustment On Interest Rate Agreements Included In Net Income Net Of Tax OtherComprehensiveIncomeReclassificationAdjustmentOnInterestRateAgreementsIncludedInNetIncomeNetOfTax	662000	USD
CY2016	ato	Other Comprehensive Income Unrealized Gain Loss On Forward Commodity Contracts Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnForwardCommodityContractsArisingDuringPeriodNetOfTax	-11662000	USD
CY2017	ato	Other Comprehensive Income Unrealized Gain Loss On Forward Commodity Contracts Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnForwardCommodityContractsArisingDuringPeriodNetOfTax	9847000	USD
CY2016	ato	Other Comprehensive Income Unrealized Gain Loss On Interest Rate Agreements Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnInterestRateAgreementsArisingDuringPeriodNetOfTax	-99029000	USD
CY2017	ato	Other Comprehensive Income Unrealized Gain Loss On Interest Rate Agreements Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnInterestRateAgreementsArisingDuringPeriodNetOfTax	74560000	USD
CY2016Q3	ato	Other Liabilities Current Other OtherLiabilitiesCurrentOther	5633000	USD
CY2017Q3	ato	Other Liabilities Current Other OtherLiabilitiesCurrentOther	5251000	USD
CY2016Q3	ato	Other Liabilities Noncurrent Other OtherLiabilitiesNoncurrentOther	33920000	USD
CY2017Q3	ato	Other Liabilities Noncurrent Other OtherLiabilitiesNoncurrentOther	36266000	USD
CY2015	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Cash Collateral PaymentsforProceedsfromHedgeFinancingActivitiesCashCollateral	0	USD
CY2016	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Cash Collateral PaymentsforProceedsfromHedgeFinancingActivitiesCashCollateral	25670000	USD
CY2017	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Cash Collateral PaymentsforProceedsfromHedgeFinancingActivitiesCashCollateral	-25670000	USD
CY2015	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Settlements PaymentsforProceedsfromHedgeFinancingActivitiesSettlements	-13364000	USD
CY2016	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Settlements PaymentsforProceedsfromHedgeFinancingActivitiesSettlements	0	USD
CY2017	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Settlements PaymentsforProceedsfromHedgeFinancingActivitiesSettlements	36996000	USD
CY2015	ato	Proceeds From Use Tax Refund Investing Activities ProceedsFromUseTaxRefundInvestingActivities	0	USD
CY2016	ato	Proceeds From Use Tax Refund Investing Activities ProceedsFromUseTaxRefundInvestingActivities	0	USD
CY2017	ato	Proceeds From Use Tax Refund Investing Activities ProceedsFromUseTaxRefundInvestingActivities	29790000	USD
CY2016Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	9958627000	USD
CY2017Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	11001910000	USD
CY2016Q3	ato	Public Utilities Property Plantand Equipment Storage PublicUtilitiesPropertyPlantandEquipmentStorage	353523000	USD
CY2017Q3	ato	Public Utilities Property Plantand Equipment Storage PublicUtilitiesPropertyPlantandEquipmentStorage	369510000	USD
CY2016	ato	Regulated Segments Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate RegulatedSegmentsEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.37
CY2017	ato	Regulated Segments Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate RegulatedSegmentsEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.37
CY2016Q3	ato	Regulatory Asset Future Recoverable Pension Costs RegulatoryAssetFutureRecoverablePensionCosts	12400000	USD
CY2015Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	5974000	USD
CY2016Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	7104000	USD
CY2017Q3	ato	Regulatory Asset Future Recoverable Pension Costs RegulatoryAssetFutureRecoverablePensionCosts	9400000	USD
CY2016Q3	ato	Regulatory Cost Of Removal Liability RegulatoryCostOfRemovalLiability	424281000	USD
CY2017Q3	ato	Regulatory Cost Of Removal Liability RegulatoryCostOfRemovalLiability	485420000	USD
CY2016Q3	ato	Regulatory Cost Of Removal Liability Current RegulatoryCostOfRemovalLiabilityCurrent	52610000	USD
CY2017Q3	ato	Regulatory Cost Of Removal Liability Current RegulatoryCostOfRemovalLiabilityCurrent	35910000	USD
CY2014Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Beginning Balance ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberBeginningBalance	988637	shares
CY2015Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Beginning Balance ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberBeginningBalance	878104	shares
CY2016Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Beginning Balance ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberBeginningBalance	782431	shares
CY2015Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Ending Balance ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberEndingBalance	878104	shares
CY2016Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Ending Balance ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberEndingBalance	782431	shares
CY2017Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Ending Balance ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberEndingBalance	570814	shares
CY2014Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Beginning Of Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueBeginningOfPeriod	42.22
CY2015Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Beginning Of Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueBeginningOfPeriod	48.24
CY2016Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Beginning Of Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueBeginningOfPeriod	57.66
CY2015Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value End Of Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueEndOfPeriod	48.24
CY2016Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value End Of Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueEndOfPeriod	57.66
CY2017Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value End Of Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueEndOfPeriod	69.45
CY2017Q3	ato	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailable	2000000	shares
CY2015	ato	Share Based Compensation Tax Benefit ShareBasedCompensationTaxBenefit	4700000	USD
CY2016	ato	Share Based Compensation Tax Benefit ShareBasedCompensationTaxBenefit	5000000	USD
CY2017	ato	Share Based Compensation Tax Benefit ShareBasedCompensationTaxBenefit	4400000	USD
CY2016Q3	ato	Term Loan Agreement Amount Outstanding TermLoanAgreementAmountOutstanding	0	USD
CY2017Q3	ato	Term Loan Agreement Amount Outstanding TermLoanAgreementAmountOutstanding	125000000	USD
CY2017Q3	ato	Term Loan Agreement Incremental Borrowings TermLoanAgreementIncrementalBorrowings	1000000	USD
CY2017Q3	ato	Term Loan Agreement Maximum Borrowing Capacity TermLoanAgreementMaximumBorrowingCapacity	200000000	USD
CY2017Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	8302000	USD
CY2017	ato	Weighted Average Cost Of Actual Heating Season Gas WeightedAverageCostOfActualHeatingSeasonGas	3.08
CY2017	dei	Amendment Flag AmendmentFlag	false
CY2017	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--09-30
CY2017	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2017	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2017
CY2017	dei	Document Period End Date DocumentPeriodEndDate	2017-09-30
CY2017	dei	Document Type DocumentType	10-K
CY2017	dei	Entity Central Index Key EntityCentralIndexKey	0000731802
CY2017Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	106112709	shares
CY2017	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2017	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2017Q1	dei	Entity Public Float EntityPublicFloat	8146262574	USD
CY2017	dei	Entity Registrant Name EntityRegistrantName	Atmos Energy Corporation
CY2017	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2017	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2016Q3	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	196485000	USD
CY2017Q3	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	233050000	USD
CY2016Q3	us-gaap	Accounts Payable And Accrued Liabilities Current And Noncurrent AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	196485000	USD
CY2017Q3	us-gaap	Accounts Payable And Accrued Liabilities Current And Noncurrent AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	233050000	USD
CY2016Q3	us-gaap	Accounts Payable Current And Noncurrent AccountsPayableCurrentAndNoncurrent	114361000	USD
CY2017Q3	us-gaap	Accounts Payable Current And Noncurrent AccountsPayableCurrentAndNoncurrent	143422000	USD
CY2016Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	226936000	USD
CY2017Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	233128000	USD
CY2016Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	215880000	USD
CY2017Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	222263000	USD
CY2016Q3	us-gaap	Accrued Employee Benefits Current AccruedEmployeeBenefitsCurrent	47058000	USD
CY2017Q3	us-gaap	Accrued Employee Benefits Current AccruedEmployeeBenefitsCurrent	46653000	USD
CY2016Q3	us-gaap	Accrued Liabilities Current And Noncurrent AccruedLiabilitiesCurrentAndNoncurrent	35017000	USD
CY2017Q3	us-gaap	Accrued Liabilities Current And Noncurrent AccruedLiabilitiesCurrentAndNoncurrent	39375000	USD
CY2016Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-188022000	USD
CY2017Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-105254000	USD
CY2016Q3	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	2388027000	USD
CY2017Q3	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	2536365000	USD
CY2015	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	27500000	USD
CY2016	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	24600000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23100000	USD
CY2016Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	11056000	USD
CY2017Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	10865000	USD
CY2015	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	5922000	USD
CY2016	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	5667000	USD
CY2017	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	6469000	USD
CY2016Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	13400000	USD
CY2017Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	12800000	USD
CY2016Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	13404000	USD
CY2017Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	12827000	USD
CY2016Q3	us-gaap	Assets Assets	10010889000	USD
CY2017Q3	us-gaap	Assets Assets	10749596000	USD
CY2016Q3	us-gaap	Assets Current AssetsCurrent	681686000	USD
CY2017Q3	us-gaap	Assets Current AssetsCurrent	539646000	USD
CY2016Q3	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	136905000	USD
CY2017Q3	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	91648000	USD
CY2016Q3	us-gaap	Assets Of Disposal Group Including Discontinued Operation Current AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent	151117000	USD
CY2017Q3	us-gaap	Assets Of Disposal Group Including Discontinued Operation Current AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent	0	USD
CY2016Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	72701000	USD
CY2017Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	88409000	USD
CY2016Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	7729000	USD
CY2017Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	11203000	USD
CY2016Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	600000	USD
CY2017Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	38000	USD
CY2016Q3	us-gaap	Available For Sale Securities Amortized Cost AvailableForSaleSecuritiesAmortizedCost	65572000	USD
CY2017Q3	us-gaap	Available For Sale Securities Amortized Cost AvailableForSaleSecuritiesAmortizedCost	77244000	USD
CY2016Q3	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	5651838000	USD
CY2017Q3	us-gaap	Capitalization Longterm Debt And Equity CapitalizationLongtermDebtAndEquity	6965711000	USD
CY2014Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	42258000	USD
CY2015Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	28653000	USD
CY2016Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	47534000	USD
CY2017Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	26409000	USD
CY2015	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-13605000	USD
CY2016	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	18881000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-21125000	USD
CY2015	us-gaap	Change In Unrealized Gain Loss On Fair Value Hedging Instruments1 ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1	10311000	USD
CY2016	us-gaap	Change In Unrealized Gain Loss On Fair Value Hedging Instruments1 ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1	3516000	USD
CY2017	us-gaap	Change In Unrealized Gain Loss On Fair Value Hedging Instruments1 ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1	-9567000	USD
CY2015	us-gaap	Change In Unrealized Gain Loss On Hedged Item In Fair Value Hedge1 ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1	-9768000	USD
CY2016	us-gaap	Change In Unrealized Gain Loss On Hedged Item In Fair Value Hedge1 ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1	18079000	USD
CY2017	us-gaap	Change In Unrealized Gain Loss On Hedged Item In Fair Value Hedge1 ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1	12858000	USD
CY2016Q3	us-gaap	Commercial Paper CommercialPaper	829800000	USD
CY2017Q3	us-gaap	Commercial Paper CommercialPaper	447700000	USD
CY2015	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.56
CY2016	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.68
CY2017	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.80
CY2016Q3	us-gaap	Common Stock No Par Value CommonStockNoParValue	0.005
CY2017Q3	us-gaap	Common Stock No Par Value CommonStockNoParValue	0.005
CY2016Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2017Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2016Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	103930560	shares
CY2017Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	106104634	shares
CY2016Q3	us-gaap	Common Stock Value CommonStockValue	520000	USD
CY2017Q3	us-gaap	Common Stock Value CommonStockValue	531000	USD
CY2015	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	218138000	USD
CY2016	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	271412000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	479189000	USD
CY2015	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	1295675000	USD
CY2015Q4	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	240326000	USD
CY2016Q1	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	377356000	USD
CY2016Q2	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	64583000	USD
CY2016Q3	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	63927000	USD
CY2016	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	746192000	USD
CY2016Q4	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	311305000	USD
CY2017Q1	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	427494000	USD
CY2017Q2	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	114176000	USD
CY2017Q3	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	72561000	USD
CY2017	us-gaap	Cost Of Natural Gas Purchases CostOfNaturalGasPurchases	925536000	USD
CY2016Q3	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	14527000	USD
CY2015	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2016	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2015	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	6513000	USD
CY2016	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	5667000	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	9022000	USD
CY2016Q3	us-gaap	Customer Advances For Construction CustomerAdvancesForConstruction	9850000	USD
CY2017Q3	us-gaap	Customer Advances For Construction CustomerAdvancesForConstruction	9309000	USD
CY2016Q3	us-gaap	Customer Deposits Current CustomerDepositsCurrent	81219000	USD
CY2017Q3	us-gaap	Customer Deposits Current CustomerDepositsCurrent	54627000	USD
CY2016Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	2460000000	USD
CY2017Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3085000000	USD
CY2017Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3085000000	USD
CY2017Q3	us-gaap	Debt Instrument Fair Value DebtInstrumentFairValue	3382272000	USD
CY2016Q3	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	4270000	USD
CY2017Q3	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	-4384000	USD
CY2015	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	170649000	USD
CY2016	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	178630000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	197013000	USD
CY2016Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	16951000	USD
CY2017Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	22339000	USD
CY2016Q3	us-gaap	Deferred Gas Cost DeferredGasCost	45184000	USD
CY2017Q3	us-gaap	Deferred Gas Cost DeferredGasCost	65714000	USD
CY2015	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	192886000	USD
CY2016	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	193556000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	227183000	USD
CY2016Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2383351000	USD
CY2017Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2643889000	USD
CY2015	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	12393000	USD
CY2016	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	12350000	USD
CY2017	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	15348000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Charitable Contribution Carryforwards DeferredTaxAssetsCharitableContributionCarryforwards	7600000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	790776000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	770593000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	107782000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	65171000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	780295000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	765190000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	514391000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	555043000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	23648000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	10218000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	122682000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	121288000	USD
CY2016Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	10481000	USD
CY2017Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	5403000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1603056000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1878699000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	1603056000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Noncurrent DeferredTaxLiabilitiesNoncurrent	1878699000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	38696000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	41927000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	2259278000	USD
CY2016Q3	us-gaap	Deferred Tax Liabilities Regulatory Assets DeferredTaxLiabilitiesRegulatoryAssets	54725000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Regulatory Assets DeferredTaxLiabilitiesRegulatoryAssets	60376000	USD
CY2015	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	14800000	USD
CY2016	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	15800000	USD
CY2017	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	15400000	USD
CY2015	us-gaap	Depreciation And Amortization DepreciationAndAmortization	272408000	USD
CY2016	us-gaap	Depreciation And Amortization DepreciationAndAmortization	290791000	USD
CY2017Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	2528485000	USD
CY2017	us-gaap	Depreciation And Amortization DepreciationAndAmortization	319448000	USD
CY2015	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	274796000	USD
CY2016	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	293096000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	319633000	USD
CY2016Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	32515000	USD
CY2017Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2016Q3	us-gaap	Derivative Assets DerivativeAssets	11626000	USD
CY2017Q3	us-gaap	Derivative Assets DerivativeAssets	3239000	USD
CY2016Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	3029000	USD
CY2017Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	2436000	USD
CY2016Q3	us-gaap	Derivative Assets Liabilities At Fair Value Net DerivativeAssetsLiabilitiesAtFairValueNet	-235968000	USD
CY2017Q3	us-gaap	Derivative Assets Liabilities At Fair Value Net DerivativeAssetsLiabilitiesAtFairValueNet	-109159000	USD
CY2016Q3	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	1822000	USD
CY2017Q3	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	803000	USD
CY2016Q3	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	6775000	USD
CY2016Q3	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	6800000	USD
CY2017Q3	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	0	USD
CY2016Q3	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	44141000	USD
CY2017Q3	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	3239000	USD
CY2016Q3	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	323684000	USD
CY2017Q3	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	112398000	USD
CY2015	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	15500000	USD
CY2016	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	-15500000	USD
CY2017	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	6800000	USD
CY2016Q3	us-gaap	Derivative Liabilities DerivativeLiabilities	240819000	USD
CY2017Q3	us-gaap	Derivative Liabilities DerivativeLiabilities	112398000	USD
CY2016Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	56771000	USD
CY2017Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	322000	USD
CY2016Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	184048000	USD
CY2017Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	112076000	USD
CY2016Q3	us-gaap	Derivative Liability Collateral Right To Reclaim Cash Offset DerivativeLiabilityCollateralRightToReclaimCashOffset	43575000	USD
CY2016Q3	us-gaap	Derivative Liability Collateral Right To Reclaim Cash Offset DerivativeLiabilityCollateralRightToReclaimCashOffset	43600000	USD
CY2017Q3	us-gaap	Derivative Liability Collateral Right To Reclaim Cash Offset DerivativeLiabilityCollateralRightToReclaimCashOffset	0	USD
CY2016Q3	us-gaap	Derivative Liability Fair Value Gross Asset And Right To Reclaim Cash Offset DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset	82865000	USD
CY2017Q3	us-gaap	Derivative Liability Fair Value Gross Asset And Right To Reclaim Cash Offset DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset	0	USD
CY2015	us-gaap	Discontinued Operation Gain Loss From Disposal Of Discontinued Operation Before Income Tax DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax	0	USD
CY2016	us-gaap	Discontinued Operation Gain Loss From Disposal Of Discontinued Operation Before Income Tax DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax	0	USD
CY2017	us-gaap	Discontinued Operation Gain Loss From Disposal Of Discontinued Operation Before Income Tax DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax	12931000	USD
CY2015	us-gaap	Discontinued Operation Gain Loss On Disposal Of Discontinued Operation Net Of Tax DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax	0	USD
CY2016	us-gaap	Discontinued Operation Gain Loss On Disposal Of Discontinued Operation Net Of Tax DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax	0	USD
CY2017	us-gaap	Discontinued Operation Gain Loss On Disposal Of Discontinued Operation Net Of Tax DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax	2716000	USD
CY2015	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Basic And Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerBasicAndDilutedShare	0.09
CY2016	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Basic And Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerBasicAndDilutedShare	0.05
CY2017	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Basic And Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerBasicAndDilutedShare	0.13
CY2016Q3	us-gaap	Disposal Group Including Discontinued Operation Assets Noncurrent DisposalGroupIncludingDiscontinuedOperationAssetsNoncurrent	28616000	USD
CY2017Q3	us-gaap	Disposal Group Including Discontinued Operation Assets Noncurrent DisposalGroupIncludingDiscontinuedOperationAssetsNoncurrent	0	USD
CY2015	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	160018000	USD
CY2016	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	175126000	USD
CY2017	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	191931000	USD
CY2015	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	3.09
CY2015Q4	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	1.00
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CY2016Q2	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.69
CY2016Q3	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.33
CY2016	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	3.38
CY2016Q4	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	1.19
CY2017Q1	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	1.55
CY2017Q2	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.67
CY2017Q3	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	0.34
CY2017	us-gaap	Earnings Per Share Basic And Diluted EarningsPerShareBasicAndDiluted	3.73
CY2015	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	11500000	USD
CY2016	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	9800000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	9000000	USD
CY2017Q3	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	10900000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y7M0D
CY2016Q3	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	179070000	USD
CY2017Q3	us-gaap	Energy Related Inventory Gas Stored Underground EnergyRelatedInventoryGasStoredUnderground	184653000	USD
CY2015	us-gaap	Gain Loss On Cash Flow Hedge Ineffectiveness Net GainLossOnCashFlowHedgeIneffectivenessNet	-325000	USD
CY2016	us-gaap	Gain Loss On Cash Flow Hedge Ineffectiveness Net GainLossOnCashFlowHedgeIneffectivenessNet	-19000	USD
CY2017	us-gaap	Gain Loss On Cash Flow Hedge Ineffectiveness Net GainLossOnCashFlowHedgeIneffectivenessNet	111000	USD
CY2015	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	0	USD
CY2016	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	0	USD
CY2017	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	10579000	USD
CY2015	us-gaap	Gain Loss On Fair Value Hedges Recognized In Earnings GainLossOnFairValueHedgesRecognizedInEarnings	543000	USD
CY2016	us-gaap	Gain Loss On Fair Value Hedges Recognized In Earnings GainLossOnFairValueHedgesRecognizedInEarnings	21595000	USD
CY2017	us-gaap	Gain Loss On Fair Value Hedges Recognized In Earnings GainLossOnFairValueHedgesRecognizedInEarnings	3291000	USD
CY2017	us-gaap	Gain On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring GainOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurring	10600000	USD
CY2016Q3	us-gaap	Goodwill Goodwill	726962000	USD
CY2017Q3	us-gaap	Goodwill Goodwill	730132000	USD
CY2017	us-gaap	Goodwill Other Increase Decrease GoodwillOtherIncreaseDecrease	-459000	USD
CY2017	us-gaap	Goodwill Transfers GoodwillTransfers	2711000	USD
CY2015	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	305623000	USD
CY2015Q4	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	101546000	USD
CY2016Q1	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	143003000	USD
CY2016Q2	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	66143000	USD
CY2016Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	34850000	USD
CY2016	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	345542000	USD
CY2016Q4	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	114038000	USD
CY2017Q1	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	162012000	USD
CY2017Q2	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	70808000	USD
CY2017Q3	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	35853000	USD
CY2017	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	382711000	USD
CY2015	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	495172000	USD
CY2016	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	542184000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	604094000	USD
CY2015	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	3.00
CY2015Q4	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	0.99
CY2016Q1	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	1.39
CY2016Q2	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	0.64
CY2016Q3	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	0.33
CY2016	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	3.33
CY2016Q4	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	1.08
CY2017Q1	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	1.52
CY2017Q2	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	0.67
CY2017Q3	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	0.34
CY2017	us-gaap	Income Loss From Continuing Operations Per Basic And Diluted Share IncomeLossFromContinuingOperationsPerBasicAndDilutedShare	3.60
CY2015	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	9452000	USD
CY2016	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	4562000	USD
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	13710000	USD
CY2015	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic And Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare	0.09
CY2016	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic And Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare	0.05
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic And Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare	0.13
CY2015	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	189549000	USD
CY2016	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	196642000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	221383000	USD
CY2016Q3	us-gaap	Income Tax Receivable IncomeTaxReceivable	5456000	USD
CY2017Q3	us-gaap	Income Tax Receivable IncomeTaxReceivable	0	USD
CY2015	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	4998000	USD
CY2016	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	1324000	USD
CY2017	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	0	USD
CY2015	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	2413000	USD
CY2016	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	2570000	USD
CY2017	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	2584000	USD
CY2015	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	173310000	USD
CY2016	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	189764000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	211433000	USD
CY2015	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	1365000	USD
CY2016	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-3009000	USD
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-3566000	USD
CY2015	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	12289000	USD
CY2016	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	11133000	USD
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	16100000	USD
CY2015	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	1802000	USD
CY2016	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	7794000	USD
CY2017	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	5264000	USD
CY2015	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-59112000	USD
CY2016	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-5195000	USD
CY2017	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	53017000	USD
CY2015	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-48240000	USD
CY2016	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	4847000	USD
CY2017	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	58696000	USD
CY2015	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-33234000	USD
CY2016	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-20577000	USD
CY2017	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	35126000	USD
CY2015	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	11951000	USD
CY2016	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	18739000	USD
CY2017	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	-9991000	USD
CY2015	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	896000	USD
CY2016	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	-44482000	USD
CY2017	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	-78651000	USD
CY2015	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	-51614000	USD
CY2016	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	24860000	USD
CY2017	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	-102254000	USD
CY2015	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	-56025000	USD
CY2016	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	14334000	USD
CY2017	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	-66056000	USD
CY2015	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	2300000	USD
CY2016	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	2800000	USD
CY2017	us-gaap	Interest Costs Capitalized InterestCostsCapitalized	2500000	USD
CY2015	us-gaap	Interest Expense InterestExpense	116241000	USD
CY2016	us-gaap	Interest Expense InterestExpense	114812000	USD
CY2017	us-gaap	Interest Expense InterestExpense	120182000	USD
CY2015	us-gaap	Interest Paid InterestPaid	151334000	USD
CY2016	us-gaap	Interest Paid InterestPaid	154748000	USD
CY2017	us-gaap	Interest Paid InterestPaid	156668000	USD
CY2016Q3	us-gaap	Interest Payable Current InterestPayableCurrent	34863000	USD
CY2017Q3	us-gaap	Interest Payable Current InterestPayableCurrent	39624000	USD
CY2015	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	-853000	USD
CY2016	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	-546000	USD
CY2017	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	-1043000	USD
CY2016Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10010889000	USD
CY2017Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10749596000	USD
CY2016Q3	us-gaap	Liabilities Current LiabilitiesCurrent	1788281000	USD
CY2017Q3	us-gaap	Liabilities Current LiabilitiesCurrent	1013443000	USD
CY2016Q3	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation Current LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent	72900000	USD
CY2017Q3	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation Current LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent	0	USD
CY2016Q3	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation Noncurrent LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent	316000	USD
CY2017Q3	us-gaap	Liabilities Of Disposal Group Including Discontinued Operation Noncurrent LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationNoncurrent	0	USD
CY2017Q3	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	1500000000	USD
CY2016Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	250000000	USD
CY2016Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	250000000	USD
CY2017Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	0	USD
CY2017Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	2510000000	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	0	USD
CY2017Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	575000000	USD
CY2016Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2188779000	USD
CY2017Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	3067045000	USD
CY2016Q3	us-gaap	Marketable Securities MarketableSecurities	72701000	USD
CY2017Q3	us-gaap	Marketable Securities MarketableSecurities	88409000	USD
CY2015	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	131083000	USD
CY2016	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	303623000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	168091000	USD
CY2015	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-956602000	USD
CY2016	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1079732000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1056306000	USD
CY2015	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	811914000	USD
CY2016	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	794990000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	867090000	USD
CY2015	us-gaap	Net Income Loss NetIncomeLoss	315075000	USD
CY2015Q4	us-gaap	Net Income Loss NetIncomeLoss	102861000	USD
CY2016Q1	us-gaap	Net Income Loss NetIncomeLoss	141810000	USD
CY2016Q2	us-gaap	Net Income Loss NetIncomeLoss	71193000	USD
CY2016Q3	us-gaap	Net Income Loss NetIncomeLoss	34240000	USD
CY2016	us-gaap	Net Income Loss NetIncomeLoss	350104000	USD
CY2016Q4	us-gaap	Net Income Loss NetIncomeLoss	125032000	USD
CY2017Q1	us-gaap	Net Income Loss NetIncomeLoss	164728000	USD
CY2017Q2	us-gaap	Net Income Loss NetIncomeLoss	70808000	USD
CY2017Q3	us-gaap	Net Income Loss NetIncomeLoss	35853000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	396421000	USD
CY2015	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	9433000	USD
CY2016	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	4554000	USD
CY2017	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	13698000	USD
CY2017	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	3	segment
CY2015	us-gaap	Operating Income Loss OperatingIncomeLoss	612232000	USD
CY2015Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	192729000	USD
CY2016Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	251656000	USD
CY2016Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	128396000	USD
CY2016Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	84449000	USD
CY2016	us-gaap	Operating Income Loss OperatingIncomeLoss	657230000	USD
CY2016Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	209918000	USD
CY2017Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	285172000	USD
CY2017Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	140664000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	114937000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	17170000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	15138000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	15238000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	15438000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	16437000	USD
CY2017Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	91792000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	727546000	USD
CY2017Q3	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	35516000	USD
CY2015	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	32500000	USD
CY2016	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	32600000	USD
CY2017	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	32700000	USD
CY2016Q3	us-gaap	Other Assets Current OtherAssetsCurrent	88085000	USD
CY2017Q3	us-gaap	Other Assets Current OtherAssetsCurrent	106321000	USD
CY2016Q3	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	7102000	USD
CY2017Q3	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	1536000	USD
CY2016Q3	us-gaap	Other Assets Miscellaneous Noncurrent OtherAssetsMiscellaneousNoncurrent	15606000	USD
CY2017Q3	us-gaap	Other Assets Miscellaneous Noncurrent OtherAssetsMiscellaneousNoncurrent	20447000	USD
CY2016Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	305019000	USD
CY2017Q3	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	220636000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-2713000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-465000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	2564000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	-78227000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	80204000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-96937000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-78692000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	82768000	USD
CY2015	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-96937000	USD
CY2016	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-78692000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	82768000	USD
CY2015	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-1559000	USD
CY2016	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-245000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	1473000	USD
CY2016Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	439085000	USD
CY2017Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	332648000	USD
CY2016Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	245374000	USD
CY2017Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	175735000	USD
CY2015	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-359000	USD
CY2016	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-1019000	USD
CY2017	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-97000	USD
CY2015	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-819000	USD
CY2016	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-234000	USD
CY2017	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-3270000	USD
CY2015	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	516406000	USD
CY2016	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	538592000	USD
CY2017	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	546798000	USD
CY2015	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-5422000	USD
CY2016	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-6460000	USD
CY2017	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-9341000	USD
CY2015	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	7985000	USD
CY2016	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	0	USD
CY2017	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	0	USD
CY2015	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	160018000	USD
CY2016	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	175126000	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	191931000	USD
CY2015	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	29527000	USD
CY2016	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	32551000	USD
CY2017	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	53597000	USD
CY2015	us-gaap	Payments To Acquire Oil And Gas Equipment PaymentsToAcquireOilAndGasEquipment	0	USD
CY2016	us-gaap	Payments To Acquire Oil And Gas Equipment PaymentsToAcquireOilAndGasEquipment	0	USD
CY2017	us-gaap	Payments To Acquire Oil And Gas Equipment PaymentsToAcquireOilAndGasEquipment	86128000	USD
CY2015	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	963621000	USD
CY2016	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1086950000	USD
CY2017	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1137089000	USD
CY2016Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	36606000	USD
CY2017Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	18411000	USD
CY2016Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	297743000	USD
CY2017Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	230588000	USD
CY2016Q3	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	21489000	USD
CY2017Q3	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	32163000	USD
CY2015	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	0	USD
CY2016	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	0	USD
CY2017	us-gaap	Proceeds From Divestiture Of Businesses ProceedsFromDivestitureOfBusinesses	140253000	USD
CY2015	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2016	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	98574000	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	98755000	USD
CY2015	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	499060000	USD
CY2016	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	884911000	USD
CY2015	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	30952000	USD
CY2016	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	34278000	USD
CY2017	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	26523000	USD
CY2015	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	6235000	USD
CY2016	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	6290000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	9332000	USD
CY2015	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-5522000	USD
CY2016	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-317000	USD
CY2017	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-6775000	USD
CY2015	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	261232000	USD
CY2016	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	371884000	USD
CY2017	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-382066000	USD
CY2015	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	24889000	USD
CY2016	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	27019000	USD
CY2017	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	31792000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	1873900000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	2042122000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Amount Of Acquisition Adjustments1 PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1	-59800000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Amount Of Acquisition Adjustments1 PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1	-64100000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Common PublicUtilitiesPropertyPlantAndEquipmentCommon	732606000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Common PublicUtilitiesPropertyPlantAndEquipmentCommon	765662000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	183879000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	299394000	USD
CY2015	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.033
CY2016	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.032
CY2017	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.031
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	6598990000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	7306021000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Generation Or Processing PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing	66000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Generation Or Processing PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing	66000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	8268606000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	9259182000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	40515000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	38980000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	10142506000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	11301304000	USD
CY2016Q3	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	2232927000	USD
CY2017Q3	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	2521671000	USD
CY2016Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	20180000	USD
CY2017Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	15559000	USD
CY2015	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	2926985000	USD
CY2015Q4	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	674753000	USD
CY2016Q1	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	890040000	USD
CY2016Q2	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	456212000	USD
CY2016Q3	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	433643000	USD
CY2016	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	2454648000	USD
CY2016Q4	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	780168000	USD
CY2017Q1	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	988186000	USD
CY2017Q2	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	526501000	USD
CY2017Q3	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	464880000	USD
CY2017	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	2759735000	USD
CY2016Q3	us-gaap	Regulatory Assets RegulatoryAssets	263623000	USD
CY2017Q3	us-gaap	Regulatory Assets RegulatoryAssets	176798000	USD
CY2016Q3	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	214890000	USD
CY2017Q3	us-gaap	Regulatory Assets Noncurrent RegulatoryAssetsNoncurrent	110977000	USD
CY2016Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	514725000	USD
CY2017Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	555657000	USD
CY2016Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	4152000	USD
CY2017Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	5257000	USD
CY2017	us-gaap	Remaining Recovery Period Of Regulatory Assets For Which No Return On Investment During Recovery Period Is Provided1 RemainingRecoveryPeriodOfRegulatoryAssetsForWhichNoReturnOnInvestmentDuringRecoveryPeriodIsProvided1	P15Y
CY2015	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	500000000	USD
CY2016	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2017	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	250000000	USD
CY2016Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1262534000	USD
CY2017Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1467024000	USD
CY2015	us-gaap	Share Based Compensation ShareBasedCompensation	15980000	USD
CY2016	us-gaap	Share Based Compensation ShareBasedCompensation	14760000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	14064000	USD
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	3388	shares
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	4860	shares
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	36788	shares
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	48.55
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	53.52
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	63.48
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	444543	shares
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	357323	shares
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	273497	shares
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	50.50
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	65.98
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	74.15
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	551688	shares
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	448136	shares
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	448326	shares
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	21700000	USD
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	20600000	USD
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	23400000	USD
CY2015	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	39.28
CY2016	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	45.88
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	52.23
CY2016Q1	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Additional Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized	2500000.0	shares
CY2015Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	8700000.0	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	11200000.0	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	11200000	shares
CY2016Q3	us-gaap	Short Term Borrowings ShortTermBorrowings	829811000	USD
CY2017Q3	us-gaap	Short Term Borrowings ShortTermBorrowings	447745000	USD
CY2015	us-gaap	Stock Issued During Period Value Employee Benefit Plan StockIssuedDuringPeriodValueEmployeeBenefitPlan	20326000	USD
CY2016	us-gaap	Stock Issued During Period Value Employee Benefit Plan StockIssuedDuringPeriodValueEmployeeBenefitPlan	25049000	USD
CY2017	us-gaap	Stock Issued During Period Value Employee Benefit Plan StockIssuedDuringPeriodValueEmployeeBenefitPlan	17552000	USD
CY2015	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	10626000	USD
CY2016	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	9229000	USD
CY2016Q3	us-gaap	Supplies Supplies	5825000	USD
CY2017	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	8971000	USD
CY2016	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	98574000	USD
CY2017	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	98755000	USD
CY2015	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	2266000	USD
CY2016	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	3178000	USD
CY2017	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	3701000	USD
CY2015	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	25212000	USD
CY2016	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	21419000	USD
CY2017	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	19370000	USD
CY2015	us-gaap	Stock Redeemed Or Called During Period Value StockRedeemedOrCalledDuringPeriodValue	7985000	USD
CY2014Q3	us-gaap	Stockholders Equity StockholdersEquity	3086232000	USD
CY2015Q3	us-gaap	Stockholders Equity StockholdersEquity	3194797000	USD
CY2016Q3	us-gaap	Stockholders Equity StockholdersEquity	3463059000	USD
CY2017Q3	us-gaap	Stockholders Equity StockholdersEquity	3898666000	USD
CY2017Q3	us-gaap	Supplies Supplies	4472000	USD
CY2015	us-gaap	Taxes Other TaxesOther	230264000	USD
CY2016	us-gaap	Taxes Other TaxesOther	221843000	USD
CY2017	us-gaap	Taxes Other TaxesOther	240407000	USD
CY2016Q3	us-gaap	Taxes Payable Current TaxesPayableCurrent	104145000	USD
CY2017Q3	us-gaap	Taxes Payable Current TaxesPayableCurrent	116291000	USD
CY2015	us-gaap	Undistributed Discontinued Operation Earnings Loss Allocation To Participating Securities Basic UndistributedDiscontinuedOperationEarningsLossAllocationToParticipatingSecuritiesBasic	19000	USD
CY2016	us-gaap	Undistributed Discontinued Operation Earnings Loss Allocation To Participating Securities Basic UndistributedDiscontinuedOperationEarningsLossAllocationToParticipatingSecuritiesBasic	8000	USD
CY2017	us-gaap	Undistributed Discontinued Operation Earnings Loss Allocation To Participating Securities Basic UndistributedDiscontinuedOperationEarningsLossAllocationToParticipatingSecuritiesBasic	12000	USD
CY2015	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	607000	USD
CY2016	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	538000	USD
CY2017	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	475000	USD
CY2014Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	12629000	USD
CY2015Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	17069000	USD
CY2016Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	20298000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	23719000	USD
CY2016	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	290000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	366000	USD
CY2015Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	800000	USD
CY2016Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	3300000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	4500000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	500000	USD
CY2016	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	2500000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	1100000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3431000	USD
CY2016	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3519000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3787000	USD
CY2015	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	1009000	USD
CY2015Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	11095000	USD
CY2016Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	13194000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	15417000	USD
CY2015	us-gaap	Weighted Average Number Of Share Outstanding Basic And Diluted WeightedAverageNumberOfShareOutstandingBasicAndDiluted	101892000	shares
CY2016	us-gaap	Weighted Average Number Of Share Outstanding Basic And Diluted WeightedAverageNumberOfShareOutstandingBasicAndDiluted	103524000	shares
CY2017	us-gaap	Weighted Average Number Of Share Outstanding Basic And Diluted WeightedAverageNumberOfShareOutstandingBasicAndDiluted	106100000	shares
CY2017	ato	Schedule Of Divisions And Service Areas ScheduleOfDivisionsAndServiceAreas	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:6px;text-align:left;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Through our distribution business, we deliver natural gas through sales and transportation arrangements to over </font><font style="font-family:inherit;font-size:10pt;">three million</font><font style="font-family:inherit;font-size:10pt;"> residential, commercial, public-authority and industrial customers through our </font><font style="font-family:inherit;font-size:10pt;">six</font><font style="font-family:inherit;font-size:10pt;"> regulated distribution divisions in the service areas described below:</font></div><div style="line-height:120%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="3" rowspan="1"></td></tr><tr><td style="width:48%;" rowspan="1" colspan="1"></td><td style="width:4%;" rowspan="1" colspan="1"></td><td style="width:48%;" rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:center;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:center;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">Service Area</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Colorado-Kansas Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Colorado, Kansas</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Kentucky/Mid-States Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Kentucky, Tennessee, Virginia</font><font style="font-family:inherit;font-size:10pt;"><sup style="vertical-align:top;line-height:120%;font-size:7pt">(1)</sup></font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Louisiana Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Louisiana</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Mid-Tex Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Texas, including the Dallas/Fort Worth metropolitan area</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Mississippi Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Mississippi</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy West Texas Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">West Texas</font></div></td></tr></table></div><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:33px;" rowspan="1" colspan="1"></td><td rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top" rowspan="1" colspan="1"><div style="line-height:120%;font-size:8pt;padding-left:9px;"><font style="font-family:inherit;font-size:8pt;">(1)</font></div></td><td style="vertical-align:top;" rowspan="1" colspan="1"><div style="line-height:120%;text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">Denotes location where we have more limited service areas.</font></div></td></tr></table></div>
CY2017	us-gaap	Derivatives Reporting Of Derivative Activity DerivativesReportingOfDerivativeActivity	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;">Financial instruments and hedging activities</font><font style="font-family:inherit;font-size:10pt;"> — We use financial instruments to mitigate commodity price risk in our </font><font style="font-family:inherit;font-size:10pt;">distribution</font><font style="font-family:inherit;font-size:10pt;"> and </font><font style="font-family:inherit;font-size:10pt;">pipeline and storage</font><font style="font-family:inherit;font-size:10pt;"> segments and to mitigate interest rate risk. The objectives and strategies for using financial instruments have been tailored to our continuing business and are discussed in Note </font><font style="font-family:inherit;font-size:10pt;">13</font><font style="font-family:inherit;font-size:10pt;">.</font></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">We record all of our financial instruments on the balance sheet at fair value</font><font style="font-family:inherit;font-size:10pt;font-style:italic;">,</font><font style="font-family:inherit;font-size:10pt;"> with changes in fair value ultimately recorded in the income statement. These financial instruments are reported as risk management assets and liabilities and are classified as current or noncurrent other assets or liabilities based upon the anticipated settlement date of the underlying financial instrument. We record the cash flow impact of our financial instruments in operating cash flows based upon their balance sheet classification.</font></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">The timing of when changes in fair value of our financial instruments are recorded in the income statement depends on whether the financial instrument has been designated and qualifies as a part of a hedging relationship or if regulatory rulings require a different accounting treatment. Changes in fair value for financial instruments that do not meet one of these criteria are recognized in the income statement as they occur.</font></div><div style="line-height:120%;padding-top:12px;text-indent:16px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-style:italic;">Financial Instruments Associated with Commodity Price Risk</font></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">In our </font><font style="font-family:inherit;font-size:10pt;">distribution</font><font style="font-family:inherit;font-size:10pt;"> segment, the costs associated with and the gains and losses arising from the use of financial instruments to mitigate commodity price risk are included in our purchased gas cost adjustment mechanisms in accordance with regulatory requirements. Therefore, changes in the fair value of these financial instruments are initially recorded as a component of deferred gas costs and recognized in the consolidated statement of income as a component of purchased gas cost when the related costs are recovered through our rates and recognized in revenue in accordance with accounting principles generally accepted in the United States. Accordingly, there is no earnings impact on our </font><font style="font-family:inherit;font-size:10pt;">distribution</font><font style="font-family:inherit;font-size:10pt;"> segment as a result of the use of financial instruments.</font></div><div style="line-height:120%;padding-top:12px;text-indent:16px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-style:italic;">Financial Instruments Associated with Interest Rate Risk</font></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">We manage interest rate risk, primarily when we plan to issue new long-term debt or to refinance existing long-term debt. We currently manage this risk through the use of forward starting interest rate swaps to fix the Treasury yield component of the interest cost associated with anticipated financings. We designate these financial instruments as cash flow hedges at the time the agreements are executed. Unrealized gains and losses associated with the instruments are recorded as a component of accumulated other comprehensive income (loss). When the instruments settle, the realized gain or loss is recorded as a component of accumulated other comprehensive income (loss) and recognized as a component of interest expense over the life of the related financing arrangement. Hedge ineffectiveness to the extent incurred is reported as a component of interest expense. As of </font><font style="font-family:inherit;font-size:10pt;">September 30, 2017</font><font style="font-family:inherit;font-size:10pt;">, </font><font style="font-family:inherit;font-size:10pt;">no</font><font style="font-family:inherit;font-size:10pt;"> cash was required to be held in margin accounts. As of </font><font style="font-family:inherit;font-size:10pt;">September 30, 2016</font><font style="font-family:inherit;font-size:10pt;">, the Company netted </font><font style="font-family:inherit;font-size:10pt;">$25.7 million</font><font style="font-family:inherit;font-size:10pt;"> of cash held in margin accounts into its current and noncurrent risk management liabilities.</font></div></div>
CY2017	us-gaap	Nature Of Operations NatureOfOperations	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:12px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-weight:bold;">Nature of Business</font></div><div style="line-height:120%;padding-top:6px;text-align:left;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Corporation (“Atmos Energy” or the “Company”) and our subsidiaries are engaged in the regulated natural gas distribution and pipeline and storage businesses. Through our distribution business, we deliver natural gas through sales and transportation arrangements to over </font><font style="font-family:inherit;font-size:10pt;">three million</font><font style="font-family:inherit;font-size:10pt;"> residential, commercial, public-authority and industrial customers through our </font><font style="font-family:inherit;font-size:10pt;">six</font><font style="font-family:inherit;font-size:10pt;"> regulated distribution divisions in the service areas described below:</font></div><div style="line-height:120%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="3" rowspan="1"></td></tr><tr><td style="width:48%;" rowspan="1" colspan="1"></td><td style="width:4%;" rowspan="1" colspan="1"></td><td style="width:48%;" rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:center;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:center;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;font-weight:bold;">Service Area</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Colorado-Kansas Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Colorado, Kansas</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Kentucky/Mid-States Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Kentucky, Tennessee, Virginia</font><font style="font-family:inherit;font-size:10pt;"><sup style="vertical-align:top;line-height:120%;font-size:7pt">(1)</sup></font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Louisiana Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Louisiana</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Mid-Tex Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Texas, including the Dallas/Fort Worth metropolitan area</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy Mississippi Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Mississippi</font></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Atmos Energy West Texas Division</font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">  </font></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"><div style="text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">West Texas</font></div></td></tr></table></div><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:33px;" rowspan="1" colspan="1"></td><td rowspan="1" colspan="1"></td></tr><tr><td style="vertical-align:top" rowspan="1" colspan="1"><div style="line-height:120%;font-size:8pt;padding-left:9px;"><font style="font-family:inherit;font-size:8pt;">(1)</font></div></td><td style="vertical-align:top;" rowspan="1" colspan="1"><div style="line-height:120%;text-align:left;font-size:8pt;"><font style="font-family:inherit;font-size:8pt;">Denotes location where we have more limited service areas.</font></div></td></tr></table><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">In addition, we transport natural gas for others through our distribution system. Our distribution business is subject to federal and state regulation and/or regulation by local authorities in each of the states in which our distribution divisions operate. Our corporate headquarters and shared-services function are located in Dallas, Texas, and our customer support centers are located in Amarillo and Waco, Texas.</font></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">Our pipeline and storage business, which is also subject to federal and state regulation, consists of the operations of our Atmos Pipeline–Texas (APT) Division and our Louisiana natural gas transmission business. The APT division transports natural gas to our Mid-Tex Division, transports natural gas for third parties and manages five underground storage reservoirs in Texas. We also provide ancillary services customary to the pipeline industry including parking arrangements, lending and sales of inventory on hand. Our natural gas transmission operations in Louisiana are comprised of a proprietary 21-mile pipeline located in New Orleans, Louisiana that is primarily used to aggregate gas supply for our distribution division in Louisiana under a long-term contract and on a more limited basis, to third parties. </font></div><div style="line-height:120%;padding-top:6px;text-indent:30px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">On October 29, 2016, we entered into a Membership Interest Purchase Agreement (the Agreement) with CenterPoint Energy Services, Inc., a subsidiary of CenterPoint Energy, Inc. (CES) to sell all of the equity interests of AEM. The transaction closed on January 3, 2017, with an effective date of </font><font style="font-family:inherit;font-size:10pt;">January 1, 2017</font><font style="font-family:inherit;font-size:10pt;">. AEM’s historical financial results are reflected in the Company’s consolidated financial statements as discontinued operations, which required retrospective application to financial information for all periods presented. Please refer to Note 15 for further information. Our discontinued natural gas marketing segment was primarily engaged in an unregulated natural gas marketing business, conducted by Atmos Energy Marketing (AEM). The natural gas marketing business operated primarily in the Midwest and Southeast and was based in Houston, Texas. This business provided natural gas management and transportation services to municipalities, regulated distribution companies, including certain divisions of Atmos Energy, and third parties.</font></div></div>
CY2017	us-gaap	Use Of Estimates UseOfEstimates	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;">Use of estimates</font><font style="font-family:inherit;font-size:10pt;"> — The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. The most significant estimates include the allowance for doubtful accounts, unbilled revenues, contingency accruals, pension and postretirement obligations, deferred income taxes, impairment of long-lived assets, risk management and trading activities, fair value measurements and the valuation of goodwill and other long-lived assets. Actual results could differ from those estimates.</font></div></div>

Files In Submission

Name	View Source	Status
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FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
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$ATO
Atmos Energy Corp Stock $ato

2017 Q3 Form 10-K Financial Statement

#000073180217000041 Filed on November 13, 2017

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

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$ATO Atmos Energy Corp Stock $ato

2017 Q3 Form 10-K Financial Statement

#000073180217000041 Filed on November 13, 2017

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATO
Atmos Energy Corp Stock $ato