$ATO
Atmos Energy Corp Stock $ato

$ato Overview Financials Valuation SEC Filings Company Website

2019 Q3 Form 10-K Financial Statement

#000073180219000037 Filed on November 12, 2019

Income Statement

Concept	2019 Q3	2018 Q3	2018 Q2
Revenue	$443.7M	$444.7M	$562.2M
YoY Change	-0.23%	-4.34%	6.79%
Cost Of Revenue	$13.70M	$43.10M	$130.9M
YoY Change	-68.21%	-40.63%	14.61%
Gross Profit	$430.0M	$401.6M	$431.4M
YoY Change	7.07%	2.37%	4.62%
Gross Profit Margin	96.92%	90.31%	76.72%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$101.0M	$92.70M	$90.60M
YoY Change	8.95%	9.32%	13.25%
% of Gross Profit	23.49%	23.08%	21.0%
Operating Expenses	$340.3M	$312.0M	$308.4M
YoY Change	9.07%	3.83%	13.55%
Operating Profit	$89.72M	$90.63M	$124.3M
YoY Change	-1.01%	-1.27%	-11.62%
Interest Expense	-$28.80M	-$24.50M	$23.35M
YoY Change	17.55%	-27.3%	-18.07%
% of Operating Profit	-32.1%	-27.03%	18.78%
Other Income/Expense, Net	$9.300M	-$1.100M	-$3.330M
YoY Change	-945.45%	-60.71%	1052.25%
Pretax Income	$70.20M	$64.10M	$97.64M
YoY Change	9.52%	15.91%	-12.72%
Income Tax	$11.80M	$18.60M	$26.45M
% Of Pretax Income	16.81%	29.02%	27.09%
Net Earnings	$58.41M	$38.75M	$71.19M
YoY Change	50.74%	8.07%	0.54%
Net Earnings / Revenue	13.16%	8.71%	12.66%
Basic Earnings Per Share	$0.49	$0.35	$0.64
Diluted Earnings Per Share	$0.49	$0.35	$0.64
COMMON SHARES
Basic Shares Outstanding	118.2M shares	111.2M shares	111.9M shares
Diluted Shares Outstanding			111.9M shares

Balance Sheet

Concept	2019 Q3	2018 Q3	2018 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$25.00M	$14.00M	$21.00M
YoY Change	78.57%	-87.81%	-70.0%
Cash & Equivalents	$24.55M	$13.77M	$20.93M
Short-Term Investments
Other Short-Term Assets	$72.77M	$46.06M	$52.37M
YoY Change	58.01%	-56.68%	-16.51%
Inventory	$130.0M	$166.0M	$126.0M
Prepaid Expenses	$38.90M	$33.23M
Receivables	$230.6M	$253.3M	$253.5M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$458.0M	$478.9M	$452.9M
YoY Change	-4.35%	-11.27%	-15.26%
LONG-TERM ASSETS
Property, Plant & Equipment	$11.79B	$10.37B	$10.07B
YoY Change	13.66%	12.01%	12.86%
Goodwill	$730.7M	$730.4M	$730.1M
YoY Change	0.04%	0.04%	0.06%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$391.2M	$294.0M	$252.8M
YoY Change	33.06%	33.26%	-18.55%
Total Long-Term Assets	$12.91B	$11.40B	$11.05B
YoY Change	13.29%	11.61%	10.94%
TOTAL ASSETS
Total Short-Term Assets	$458.0M	$478.9M	$452.9M
Total Long-Term Assets	$12.91B	$11.40B	$11.05B
Total Assets	$13.37B	$11.87B	$11.51B
YoY Change	12.57%	10.46%	9.61%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$265.0M	$217.0M	$198.0M
YoY Change	22.12%	-6.87%	20.73%
Accrued Expenses
YoY Change
Deferred Revenue	$54.62M
YoY Change
Short-Term Debt	$464.9M	$575.8M	$244.8M
YoY Change	-19.25%	28.6%	-5.34%
Long-Term Debt Due	$0.00	$575.0M	$450.0M
YoY Change	-100.0%
Total Short-Term Liabilities	$1.209B	$1.915B	$1.466B
YoY Change	-36.85%	88.97%	96.6%
LONG-TERM LIABILITIES
Long-Term Debt	$3.529B	$2.494B	$2.618B
YoY Change	41.54%	-18.69%	-14.62%
Other Long-Term Liabilities	$400.2M	$158.0M	$74.72M
YoY Change	153.26%	-10.08%	-55.82%
Total Long-Term Liabilities	$3.930B	$2.652B	$2.693B
YoY Change	48.19%	-18.23%	-16.78%
TOTAL LIABILITIES
Total Short-Term Liabilities	$1.209B	$1.915B	$1.466B
Total Long-Term Liabilities	$3.930B	$2.652B	$2.693B
Total Liabilities	$5.139B	$4.567B	$4.159B
YoY Change	12.53%	7.3%	4.46%
SHAREHOLDERS EQUITY
Retained Earnings	$2.152B	$1.878B	$1.871B
YoY Change	14.58%	28.02%	26.44%
Common Stock	$3.713B	$2.975B	$2.965B
YoY Change	24.78%	17.29%	17.35%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$5.750B	$4.770B	$4.760B
YoY Change
Total Liabilities & Shareholders Equity	$13.37B	$11.87B	$11.51B
YoY Change	12.57%	10.46%	9.61%

Cashflow Statement

Concept	2019 Q3	2018 Q3	2018 Q2
OPERATING ACTIVITIES
Net Income	$58.41M	$38.75M	$71.19M
YoY Change	50.74%	8.07%	0.54%
Depreciation, Depletion And Amortization	$101.0M	$92.70M	$90.60M
YoY Change	8.95%	9.32%	13.25%
Cash From Operating Activities	$159.9M	$89.40M	$283.9M
YoY Change	78.86%	-26.42%	46.64%
INVESTING ACTIVITIES
Capital Expenditures	-$494.3M	-$379.1M	-$394.5M
YoY Change	30.39%	16.65%	56.11%
Acquisitions
YoY Change
Other Investing Activities	$6.000M	$2.800M	-$4.600M
YoY Change	114.29%	-82.5%	-120.81%
Cash From Investing Activities	-$488.3M	-$376.4M	-$399.1M
YoY Change	29.73%	21.85%	73.0%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	306.8M	279.9M	65.00M
YoY Change	9.61%	94.24%	5.69%
NET CHANGE
Cash From Operating Activities	159.9M	89.40M	283.9M
Cash From Investing Activities	-488.3M	-376.4M	-399.1M
Cash From Financing Activities	306.8M	279.9M	65.00M
Net Change In Cash	-21.60M	-7.100M	-50.20M
YoY Change	204.23%	-83.6%	-305.74%
FREE CASH FLOW
Cash From Operating Activities	$159.9M	$89.40M	$283.9M
Capital Expenditures	-$494.3M	-$379.1M	-$394.5M
Free Cash Flow	$654.2M	$468.5M	$678.4M
YoY Change	39.64%	4.93%	52.01%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2018Q3	ato	Derivative Cash Collateral DerivativeCashCollateral	0	USD
CY2017	ato	Other Comprehensive Income Loss Commodity Contract Derivatives Qualifyingas Hedges Tax OtherComprehensiveIncomeLossCommodityContractDerivativesQualifyingasHedgesTax	3183000	USD
CY2018	ato	Other Comprehensive Income Loss Commodity Contract Derivatives Qualifyingas Hedges Tax OtherComprehensiveIncomeLossCommodityContractDerivativesQualifyingasHedgesTax	0	USD
CY2019	ato	Other Comprehensive Income Loss Commodity Contract Derivatives Qualifyingas Hedges Tax OtherComprehensiveIncomeLossCommodityContractDerivativesQualifyingasHedgesTax	0	USD
CY2017	ato	Other Comprehensive Income Loss Interest Rate Contract Derivatives Qualifyingas Hedges Tax OtherComprehensiveIncomeLossInterestRateContractDerivativesQualifyingasHedgesTax	43238000	USD
CY2018	ato	Other Comprehensive Income Loss Interest Rate Contract Derivatives Qualifyingas Hedges Tax OtherComprehensiveIncomeLossInterestRateContractDerivativesQualifyingasHedgesTax	13017000	USD
CY2019	ato	Other Comprehensive Income Loss Interest Rate Contract Derivatives Qualifyingas Hedges Tax OtherComprehensiveIncomeLossInterestRateContractDerivativesQualifyingasHedgesTax	-6782000	USD
CY2019	dei	Amendment Flag AmendmentFlag	false
CY2019	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--09-30
CY2019	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2019	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
CY2019	dei	Entity Central Index Key EntityCentralIndexKey	0000731802
CY2017	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.80
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.94
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	2.10
CY2018Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.005
CY2019Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.005
CY2018Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2019Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2018Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	111273683	shares
CY2019Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	119338925	shares
CY2018Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	111273683	shares
CY2019Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	119338925	shares
CY2017	us-gaap	Discontinued Operation Tax Effect Of Discontinued Operation DiscontinuedOperationTaxEffectOfDiscontinuedOperation	6841000	USD
CY2018	us-gaap	Discontinued Operation Tax Effect Of Discontinued Operation DiscontinuedOperationTaxEffectOfDiscontinuedOperation	0	USD
CY2019	us-gaap	Discontinued Operation Tax Effect Of Discontinued Operation DiscontinuedOperationTaxEffectOfDiscontinuedOperation	0	USD
CY2017	us-gaap	Discontinued Operation Tax Effect Of Income Loss From Disposal Of Discontinued Operation DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation	10215000	USD
CY2018	us-gaap	Discontinued Operation Tax Effect Of Income Loss From Disposal Of Discontinued Operation DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation	0	USD
CY2019	us-gaap	Discontinued Operation Tax Effect Of Income Loss From Disposal Of Discontinued Operation DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation	0	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	1473000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-146000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	64000	USD
CY2019	dei	Document Type DocumentType	10-K
CY2019	dei	Document Annual Report DocumentAnnualReport	true
CY2019	dei	Document Period End Date DocumentPeriodEndDate	2019-09-30
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity File Number EntityFileNumber	1-10042
CY2019	dei	Entity Registrant Name EntityRegistrantName	Atmos Energy Corp
CY2019	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	TX
CY2019	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	75-1743247
CY2019	dei	Entity Address Address Line1 EntityAddressAddressLine1	1800 Three Lincoln Centre
CY2019	dei	Entity Address Address Line2 EntityAddressAddressLine2	5430 LBJ Freeway
CY2019	dei	Entity Address City Or Town EntityAddressCityOrTown	Dallas
CY2019	dei	Entity Address State Or Province EntityAddressStateOrProvince	TX
CY2019	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	75240
CY2019	dei	City Area Code CityAreaCode	972
CY2019	dei	Local Phone Number LocalPhoneNumber	934-9227
CY2019	dei	Security12b Title Security12bTitle	Common stock
CY2019	dei	Trading Symbol TradingSymbol	ATO
CY2019	dei	Security Exchange Name SecurityExchangeName	NYSE
CY2019	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2019	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2019	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2019	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2019	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2019	dei	Entity Small Business EntitySmallBusiness	false
CY2019	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2019	dei	Entity Shell Company EntityShellCompany	false
CY2019Q1	dei	Entity Public Float EntityPublicFloat	11826627172	USD
CY2019Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	119343545	shares
CY2019Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	13758899000	USD
CY2018Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	12217648000	USD
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CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	14180593000	USD
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CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.13
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.36
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.43
CY2014Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.73
CY2019	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	4.35
CY2018	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	5.43
CY2017	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	3.60
CY2019	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerDilutedShare	0
CY2018	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerDilutedShare	0
CY2017	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerDilutedShare	0.13
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.35
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.43
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.73
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	117200000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	106100000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	117461000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	106100000	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	511406000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	603064000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	396421000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	218000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-395000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	2564000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	-22944000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	44936000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	75222000	USD
CY2019	ato	Other Comprehensive Income Loss Commodity Contract Derivatives Qualifyingas Hedges Netof Tax OtherComprehensiveIncomeLossCommodityContractDerivativesQualifyingasHedgesNetofTax	0	USD
CY2018	ato	Other Comprehensive Income Loss Commodity Contract Derivatives Qualifyingas Hedges Netof Tax OtherComprehensiveIncomeLossCommodityContractDerivativesQualifyingasHedgesNetofTax	0	USD
CY2017	ato	Other Comprehensive Income Loss Commodity Contract Derivatives Qualifyingas Hedges Netof Tax OtherComprehensiveIncomeLossCommodityContractDerivativesQualifyingasHedgesNetofTax	4982000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-22726000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	44541000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	82768000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	488680000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	647605000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	479189000	USD
CY2016Q3	us-gaap	Stockholders Equity StockholdersEquity	3463059000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	396421000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	82768000	USD
CY2017	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	191931000	USD
CY2017	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	98755000	USD
CY2017	us-gaap	Stock Issued During Period Value Other StockIssuedDuringPeriodValueOther	8971000	USD
CY2017	us-gaap	Stock Issued During Period Value Employee Benefit Plan StockIssuedDuringPeriodValueEmployeeBenefitPlan	17552000	USD
CY2017	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	3701000	USD
CY2017	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	19370000	USD
CY2017Q3	us-gaap	Stockholders Equity StockholdersEquity	3898666000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	603064000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	44541000	USD
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	214906000	USD
CY2018	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	395092000	USD
CY2018	us-gaap	Stock Issued During Period Value Other StockIssuedDuringPeriodValueOther	11323000	USD
CY2018	us-gaap	Stock Issued During Period Value Employee Benefit Plan StockIssuedDuringPeriodValueEmployeeBenefitPlan	8240000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	3471000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	20460000	USD
CY2018Q3	us-gaap	Stockholders Equity StockholdersEquity	4769951000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	511406000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-22726000	USD
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	245717000	USD
CY2019	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	694103000	USD
CY2019	us-gaap	Stock Issued During Period Value Other StockIssuedDuringPeriodValueOther	11071000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Benefit Plan StockIssuedDuringPeriodValueEmployeeBenefitPlan	8252000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	2948000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	20935000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	5750223000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	511406000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	603064000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	396421000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	391456000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	361083000	USD
CY2017	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	319633000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	132004000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	158271000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	227183000	USD
CY2019	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	-158782000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Discontinued Operation Gain Loss From Disposal Of Discontinued Operation Before Income Tax DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax	0	USD
CY2018	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
CY2019	us-gaap	Gain On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring GainOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurring	0	USD
CY2018	us-gaap	Gain On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring GainOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurring	0	USD
CY2017	us-gaap	Gain On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring GainOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurring	10579000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	11121000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	12863000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	14064000	USD
CY2019	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	9464000	USD
CY2018	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	7865000	USD
CY2017	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	6469000	USD
CY2019	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	11165000	USD
CY2018	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	0	USD
CY2017	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	0	USD
CY2019	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-1169000	USD
CY2018	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-5437000	USD
CY2017	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-97000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-18724000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	29208000	USD
CY2017	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	58696000	USD
CY2019	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-35594000	USD
CY2018	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	-18921000	USD
CY2017	us-gaap	Increase Decrease In Inventories IncreaseDecreaseInInventories	35126000	USD
CY2019	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	26590000	USD
CY2018	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	-60424000	USD
CY2017	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	-9991000	USD
CY2019	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	58403000	USD
CY2018	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	10049000	USD
CY2017	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	-102254000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	9908000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-11857000	USD
CY2017	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	53017000	USD
CY2019	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	-103895000	USD
CY2018	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	74707000	USD
CY2017	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	-78651000	USD
CY2019	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	47976000	USD
CY2018	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	31923000	USD
CY2017	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	-66056000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	968769000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1124662000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	867090000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1693477000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1467591000	USD
CY2017	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1137089000	USD
CY2019	us-gaap	Payments To Acquire Oil And Gas Equipment PaymentsToAcquireOilAndGasEquipment	0	USD
CY2018	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
CY2019	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	4000000	USD
CY2018	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	3000000	USD
CY2017	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	140253000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	29153000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	46401000	USD
CY2017	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	53597000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	6070000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	22360000	USD
CY2017	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	31792000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	20299000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	15716000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	9332000	USD
CY2019	ato	Proceeds From Use Tax Refund Investing Activities ProceedsFromUseTaxRefundInvestingActivities	0	USD
CY2018	ato	Proceeds From Use Tax Refund Investing Activities ProceedsFromUseTaxRefundInvestingActivities	790000	USD
CY2017	ato	Proceeds From Use Tax Refund Investing Activities ProceedsFromUseTaxRefundInvestingActivities	29790000	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-8601000	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-8560000	USD
CY2017	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-9341000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1683660000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1463566000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1056306000	USD
CY2019	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-110865000	USD
CY2018	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	128035000	USD
CY2017	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-382066000	USD
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	1045221000	USD
CY2018	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
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	694103000	USD
CY2018	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	395092000	USD
CY2017	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	98755000	USD
CY2019	us-gaap	Proceeds From Issuance Or Sale Of Equity ProceedsFromIssuanceOrSaleOfEquity	19323000	USD
CY2018	us-gaap	Proceeds From Issuance Or Sale Of Equity ProceedsFromIssuanceOrSaleOfEquity	19563000	USD
CY2017	us-gaap	Proceeds From Issuance Or Sale Of Equity ProceedsFromIssuanceOrSaleOfEquity	26523000	USD
CY2019	us-gaap	Payments For Proceeds From Hedge Financing Activities PaymentsForProceedsFromHedgeFinancingActivities	90141000	USD
CY2018	us-gaap	Payments For Proceeds From Hedge Financing Activities PaymentsForProceedsFromHedgeFinancingActivities	0	USD
CY2017	us-gaap	Payments For Proceeds From Hedge Financing Activities PaymentsForProceedsFromHedgeFinancingActivities	36996000	USD
CY2019	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Cash Collateral PaymentsforProceedsfromHedgeFinancingActivitiesCashCollateral	0	USD
CY2018	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Cash Collateral PaymentsforProceedsfromHedgeFinancingActivitiesCashCollateral	0	USD
CY2017	ato	Paymentsfor Proceedsfrom Hedge Financing Activities Cash Collateral PaymentsforProceedsfromHedgeFinancingActivitiesCashCollateral	-25670000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	575000000	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2017	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	250000000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	245717000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	214906000	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	191931000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	11254000	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
CY2017	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	6775000	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	0	USD
CY2018	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1518000	USD
CY2017	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	0	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	725670000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	326266000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	168091000	USD
CY2019	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	10779000	USD
CY2018	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-12638000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-21125000	USD
CY2018Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	13771000	USD
CY2017Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	26409000	USD
CY2016Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	47534000	USD
CY2019Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	24550000	USD
CY2018Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	13771000	USD
CY2017Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	26409000	USD
CY2019	us-gaap	Nature Of Operations NatureOfOperations	Nature of Business<div style="line-height:120%;padding-top:6px;text-align:left;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Corporation (“Atmos Energy” or the “Company”) and its 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 </span><span style="font-family:inherit;font-size:10pt;"><span>three million</span></span><span style="font-family:inherit;font-size:10pt;"> residential, commercial, public-authority and industrial customers through our </span><span style="font-family:inherit;font-size:10pt;"><span>six</span></span><span style="font-family:inherit;font-size:10pt;"> regulated distribution divisions in the service areas described below:</span></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"/></tr><tr><td style="width:48%;"/><td style="width:4%;"/><td style="width:48%;"/></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Service Area</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Colorado-Kansas Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Colorado, Kansas</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Kentucky/Mid-States Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Kentucky, Tennessee, Virginia</span><span style="font-family:inherit;font-size:10pt;"><sup style="vertical-align:top;line-height:120%;font-size:7pt">(1)</sup></span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Louisiana Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Louisiana</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Mid-Tex Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Texas, including the Dallas/Fort Worth metropolitan area</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Mississippi Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Mississippi</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy West Texas Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">West Texas</span></div></td></tr></table></div><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:33px;"/><td/></tr><tr><td style="vertical-align:top"><div style="line-height:120%;font-size:8pt;padding-left:9px;"><span style="font-family:inherit;font-size:8pt;">(1)</span></div></td><td style="vertical-align:top;"><div style="line-height:120%;text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Denotes location where we have more limited service areas.</span></div></td></tr></table><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span 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.</span></div>Our pipeline and storage business, which is also subject to federal and state regulation, consists of the the pipeline and storage operations of our Atmos Pipeline–Texas (APT) Division and our natural gas transmission business in Louisiana. The APT division provides transportation and storage services to our Mid-Tex Division, other third-party local distribution companies, industrial and electric generation customers, as well as marketers and producers. As part of its pipeline operations, APT manages five underground storage facilities 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 21-mile pipeline located in the New Orleans, Louisiana area 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.
CY2019	ato	Schedule Of Divisions And Service Areas ScheduleOfDivisionsAndServiceAreas	Through our distribution business, we deliver natural gas through sales and transportation arrangements to over <span style="font-family:inherit;font-size:10pt;"><span>three million</span></span><span style="font-family:inherit;font-size:10pt;"> residential, commercial, public-authority and industrial customers through our </span><span style="font-family:inherit;font-size:10pt;"><span>six</span></span><span style="font-family:inherit;font-size:10pt;"> regulated distribution divisions in the service areas described below:</span><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"/></tr><tr><td style="width:48%;"/><td style="width:4%;"/><td style="width:48%;"/></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Service Area</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Colorado-Kansas Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Colorado, Kansas</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Kentucky/Mid-States Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Kentucky, Tennessee, Virginia</span><span style="font-family:inherit;font-size:10pt;"><sup style="vertical-align:top;line-height:120%;font-size:7pt">(1)</sup></span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Louisiana Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Louisiana</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Mid-Tex Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Texas, including the Dallas/Fort Worth metropolitan area</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy Mississippi Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Mississippi</span></div></td></tr><tr><td style="vertical-align:top;background-color:;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Atmos Energy West Texas Division</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">West Texas</span></div></td></tr></table></div><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div><div style="line-height:120%;font-size:8pt;padding-left:9px;"><span style="font-family:inherit;font-size:8pt;">(1)</span></div><div style="line-height:120%;text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Denotes location where we have more limited service areas.</span></div>
CY2019Q3	ato	Number Of Customers Regulated Distribution NumberOfCustomersRegulatedDistribution	3000000000000	customer
CY2019Q3	ato	Number Of Divisions Regulated Distribution NumberOfDivisionsRegulatedDistribution	6	regulated_distribution_division
CY2019	us-gaap	Use Of Estimates UseOfEstimates	<div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;">Use of estimates</span><span 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.</span></div>
CY2019Q3	us-gaap	Regulatory Assets RegulatoryAssets	284547000	USD
CY2018Q3	us-gaap	Regulatory Assets RegulatoryAssets	143811000	USD
CY2019Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	1386126000	USD
CY2018Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	1510997000	USD
CY2019	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	7643000	USD
CY2018	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	6810000	USD
CY2017	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	2479000	USD
CY2019	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	11165000	USD
CY2018	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	0	USD
CY2017	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	0	USD
CY2019	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	18808000	USD
CY2018	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	6810000	USD
CY2017	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	2479000	USD
CY2019	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.031
CY2018	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
CY2019Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	17100000	USD
CY2018Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	12900000	USD
CY2019Q3	ato	Asset Retirement Costs In Property Plant And Equipment AssetRetirementCostsInPropertyPlantAndEquipment	11300000	USD
CY2018Q3	ato	Asset Retirement Costs In Property Plant And Equipment AssetRetirementCostsInPropertyPlantAndEquipment	7500000	USD
CY2019	us-gaap	Derivatives Reporting Of Derivative Activity DerivativesReportingOfDerivativeActivity	<div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-style:italic;font-weight:bold;">Financial instruments and hedging activities</span><span style="font-family:inherit;font-size:10pt;"> — We currently use financial instruments to mitigate commodity price risk in our </span><span style="font-family:inherit;font-size:10pt;">distribution</span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;">pipeline and storage</span><span style="font-family:inherit;font-size:10pt;"> segments and in the past have also used financial instruments to mitigate interest rate risk. The objectives and strategies for using financial instruments have been tailored to our business and are discussed in Note </span><span style="font-family:inherit;font-size:10pt;">14</span><span style="font-family:inherit;font-size:10pt;">.</span></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">We record all of our financial instruments on the balance sheet at fair value</span><span style="font-family:inherit;font-size:10pt;font-style:italic;">,</span><span style="font-family:inherit;font-size:10pt;"> with changes in fair value ultimately recorded in the statement of comprehensive income. 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.</span></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">The timing of when changes in fair value of our financial instruments are recorded in the statement of comprehensive income 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 statement of comprehensive income as they occur.</span></div><div style="line-height:120%;padding-top:12px;text-indent:16px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-style:italic;">Financial Instruments Associated with Commodity Price Risk</span></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In our </span><span style="font-family:inherit;font-size:10pt;">distribution</span><span style="font-family:inherit;font-size:10pt;"> segment, the costs associated with and the realized 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 statements of comprehensive 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 </span><span style="font-family:inherit;font-size:10pt;">distribution</span><span style="font-family:inherit;font-size:10pt;"> segment as a result of the use of these financial instruments.</span></div><div style="line-height:120%;padding-top:12px;text-indent:16px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-style:italic;">Financial Instruments Associated with Interest Rate Risk</span></div><div style="line-height:120%;padding-top:6px;text-indent:32px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In connection with the planned issuance of long-term debt, we may use financial instruments to manage interest rate risk. We historically managed 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 charges over the life of the related financing arrangement. Hedge ineffectiveness to the extent incurred is reported as a component of interest charges. As of </span><span style="font-family:inherit;font-size:10pt;">September 30, 2019</span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;">September 30, 2018</span><span style="font-family:inherit;font-size:10pt;">, </span><span style="font-family:inherit;font-size:10pt;"><span>no</span></span><span style="font-family:inherit;font-size:10pt;"> cash was required to be held in margin accounts.</span></div>
CY2019Q3	ato	Derivative Cash Collateral DerivativeCashCollateral	0	USD
CY2018Q4	us-gaap	New Accounting Pronouncement Or Change In Accounting Principle Cumulative Effect Of Change On Equity Or Net Assets1 NewAccountingPronouncementOrChangeInAccountingPrincipleCumulativeEffectOfChangeOnEquityOrNetAssets1	8200000	USD
CY2019	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2019Q3	us-gaap	Number Of States In Which Entity Operates NumberOfStatesInWhichEntityOperates	8	state
CY2019	us-gaap	Revenues Revenues	2901848000	USD
CY2019	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	630308000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	391456000	USD
CY2019	us-gaap	Taxes Other TaxesOther	275189000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	746058000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	7404000	USD
CY2019	us-gaap	Interest Expense InterestExpense	103153000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	650309000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	138903000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	511406000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1693477000	USD
CY2018	us-gaap	Revenues Revenues	3115546000	USD
CY2018	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	594795000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	361083000	USD
CY2018	us-gaap	Taxes Other TaxesOther	263886000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	727934000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-10144000	USD
CY2018	us-gaap	Interest Expense InterestExpense	106646000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	611144000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	8080000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	603064000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1467591000	USD
CY2017	us-gaap	Revenues Revenues	2759735000	USD
CY2017	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	538716000	USD
CY2017	us-gaap	Depreciation And Amortization DepreciationAndAmortization	319448000	USD
CY2017	us-gaap	Taxes Other TaxesOther	240407000	USD
CY2017	us-gaap	Operating Income Loss OperatingIncomeLoss	735628000	USD
CY2017	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-11352000	USD
CY2017	us-gaap	Interest Expense InterestExpense	120182000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	604094000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	221383000	USD
CY2017	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	382711000	USD
CY2017	us-gaap	Discontinued Operation Income Loss From Discontinued Operation During Phase Out Period Net Of Tax DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodNetOfTax	10994000	USD
CY2017	us-gaap	Discontinued Operation Gain Loss On Disposal Of Discontinued Operation Net Of Tax DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax	2716000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	396421000	USD
CY2017	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1137089000	USD
CY2019	us-gaap	Regulated Operating Revenue RegulatedOperatingRevenue	2901848000	USD
CY2018	us-gaap	Regulated Operating Revenue RegulatedOperatingRevenue	3115546000	USD
CY2017	us-gaap	Regulated Operating Revenue RegulatedOperatingRevenue	2759735000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	11787669000	USD
CY2019Q3	us-gaap	Assets Assets	13367619000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	10371147000	USD
CY2018Q3	us-gaap	Assets Assets	11874437000	USD
CY2019	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	511406000	USD
CY2018	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	603064000	USD
CY2017	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	382711000	USD
CY2019	us-gaap	Undistributed Continuing Operation Earnings Loss Allocation To Participating Securities Basic UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesBasic	416000	USD
CY2018	us-gaap	Undistributed Continuing Operation Earnings Loss Allocation To Participating Securities Basic UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesBasic	580000	USD
CY2017	us-gaap	Undistributed Continuing Operation Earnings Loss Allocation To Participating Securities Basic UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesBasic	475000	USD
CY2019	us-gaap	Net Income Loss From Continuing Operations Available To Common Shareholders Basic NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic	510990000	USD
CY2018	us-gaap	Net Income Loss From Continuing Operations Available To Common Shareholders Basic NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic	602484000	USD
CY2017	us-gaap	Net Income Loss From Continuing Operations Available To Common Shareholders Basic NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic	382236000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	117200000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	106100000	shares
CY2019	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	4.36
CY2018	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	5.43
CY2017	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	3.60
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	0	USD
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	0	USD
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	13710000	USD
CY2019	us-gaap	Undistributed Discontinued Operation Earnings Loss Allocation To Participating Securities Basic UndistributedDiscontinuedOperationEarningsLossAllocationToParticipatingSecuritiesBasic	0	USD
CY2018	us-gaap	Undistributed Discontinued Operation Earnings Loss Allocation To Participating Securities Basic UndistributedDiscontinuedOperationEarningsLossAllocationToParticipatingSecuritiesBasic	0	USD
CY2017	us-gaap	Undistributed Discontinued Operation Earnings Loss Allocation To Participating Securities Basic UndistributedDiscontinuedOperationEarningsLossAllocationToParticipatingSecuritiesBasic	12000	USD
CY2019	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	0	USD
CY2018	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	0	USD
CY2017	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	13698000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	117200000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	106100000	shares
CY2019	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2018	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0
CY2017	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	0.13
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.36
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.43
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.73
CY2019	us-gaap	Net Income Loss From Continuing Operations Available To Common Shareholders Basic NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic	510990000	USD
CY2018	us-gaap	Net Income Loss From Continuing Operations Available To Common Shareholders Basic NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic	602484000	USD
CY2017	us-gaap	Net Income Loss From Continuing Operations Available To Common Shareholders Basic NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersBasic	382236000	USD
CY2019	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	USD
CY2018	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	USD
CY2017	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	510990000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	602484000	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	382236000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	117200000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	106100000	shares
CY2019	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	4.35
CY2018	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	5.43
CY2019	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	261000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	0	shares
CY2017	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	0	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	117461000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	106100000	shares
CY2017	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	3.60
CY2019	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	0	USD
CY2018	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	0	USD
CY2017	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Basic NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersBasic	13698000	USD
CY2019	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	USD
CY2018	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	USD
CY2017	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	USD
CY2019	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Diluted NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersDiluted	0	USD
CY2018	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Diluted NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersDiluted	0	USD
CY2017	us-gaap	Net Income Loss From Discontinued Operations Available To Common Shareholders Diluted NetIncomeLossFromDiscontinuedOperationsAvailableToCommonShareholdersDiluted	13698000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	117200000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	106100000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	261000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	0	shares
CY2017	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	0	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	117461000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	111012000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	106100000	shares
CY2019	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerDilutedShare	0
CY2018	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerDilutedShare	0
CY2017	us-gaap	Discontinued Operation Income Loss From Discontinued Operation Net Of Tax Per Diluted Share DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTaxPerDilutedShare	0.13
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.35
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.43
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.73
CY2019Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3560000000	USD
CY2018Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3085000000	USD
CY2019Q3	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	193000	USD
CY2018Q3	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	-4439000	USD
CY2019Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	0	USD
CY2018Q3	us-gaap	Long Term Debt Current LongTermDebtCurrent	575000000	USD
CY2019Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	30355000	USD
CY2018Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	20774000	USD
CY2019Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	3529452000	USD
CY2018Q3	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	2493665000	USD
CY2019Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2019Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	0	USD
CY2019Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	0	USD
CY2019Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2019Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	0	USD
CY2019Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	3560000000	USD
CY2019Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3560000000	USD
CY2019Q3	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	1500000000	USD
CY2019	us-gaap	Public Utilities Approved Debt Capital Structure Percentage PublicUtilitiesApprovedDebtCapitalStructurePercentage	0.70
CY2019	ato	Public Utilities Actual Debt Capital Structure Percentage PublicUtilitiesActualDebtCapitalStructurePercentage	0.42
CY2018Q3	us-gaap	Forward Contract Indexed To Issuers Equity Settlement Alternatives Shares At Fair Value ForwardContractIndexedToIssuersEquitySettlementAlternativesSharesAtFairValue	0	shares
CY2018	us-gaap	Forward Contract Indexed To Issuers Equity Forward Rate ForwardContractIndexedToIssuersEquityForwardRate	0
CY2018Q4	us-gaap	Forward Contract Indexed To Issuers Equity Shares ForwardContractIndexedToIssuersEquityShares	2668464	shares
CY2018Q4	us-gaap	Forward Contract Indexed To Issuers Equity Forward Rate ForwardContractIndexedToIssuersEquityForwardRate	91.77
CY2019Q1	us-gaap	Forward Contract Indexed To Issuers Equity Shares ForwardContractIndexedToIssuersEquityShares	1670509	shares
CY2019Q1	us-gaap	Forward Contract Indexed To Issuers Equity Forward Rate ForwardContractIndexedToIssuersEquityForwardRate	95.46
CY2019Q2	us-gaap	Forward Contract Indexed To Issuers Equity Shares ForwardContractIndexedToIssuersEquityShares	1050563	shares
CY2019Q2	us-gaap	Forward Contract Indexed To Issuers Equity Forward Rate ForwardContractIndexedToIssuersEquityForwardRate	101.41
CY2019Q2	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	1089700	shares
CY2019Q2	ato	Stock Issued During Period New Issues Per Share StockIssuedDuringPeriodNewIssuesPerShare	91.44
CY2019Q3	us-gaap	Forward Contract Indexed To Issuers Equity Shares ForwardContractIndexedToIssuersEquityShares	1423599	shares
CY2019Q3	us-gaap	Forward Contract Indexed To Issuers Equity Forward Rate ForwardContractIndexedToIssuersEquityForwardRate	108.70
CY2019Q3	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	1093575	shares
CY2019Q3	ato	Stock Issued During Period New Issues Per Share StockIssuedDuringPeriodNewIssuesPerShare	91.78
CY2019Q3	us-gaap	Forward Contract Indexed To Issuers Equity Settlement Alternatives Shares At Fair Value ForwardContractIndexedToIssuersEquitySettlementAlternativesSharesAtFairValue	4629860	shares
CY2019	us-gaap	Remaining Recovery Period Of Regulatory Assets For Which No Return On Investment During Recovery Period Is Provided1 RemainingRecoveryPeriodOfRegulatoryAssetsForWhichNoReturnOnInvestmentDuringRecoveryPeriodIsProvided1	P15Y
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23900000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23900000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23100000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	12800000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	11100000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	9000000.0	USD
CY2019	ato	Share Based Compensation Tax Benefit ShareBasedCompensationTaxBenefit	700000	USD
CY2018	ato	Share Based Compensation Tax Benefit ShareBasedCompensationTaxBenefit	2300000	USD
CY2017	ato	Share Based Compensation Tax Benefit ShareBasedCompensationTaxBenefit	4400000	USD
CY2019Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	11200000	shares
CY2019Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	1500000	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period1 ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1	P3Y
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period1 ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1	P3Y
CY2018Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	538592	shares
CY2018Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	80.91
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	570814	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	69.45
CY2016Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	782431	shares
CY2016Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	57.66
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	241472	shares
CY2019	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	98.25
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	248710	shares
CY2018	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	85.62
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	273497	shares
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
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	269347	shares
CY2019	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	76.71
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	274392	shares
CY2018	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	64.43
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	448326	shares
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
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	7645	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	86.37
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	6540	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	74.87
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	36788	shares
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
CY2019Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	503072	shares
CY2019Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	91.66
CY2018Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	538592	shares
CY2018Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	80.91
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	570814	shares
CY2017Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	69.45
CY2019Q3	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	13700000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y7M6D
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	20500000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	17200000	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
CY2019Q3	ato	Minimum Initial Investment For Direct Stock Purchase Plan MinimumInitialInvestmentForDirectStockPurchasePlan	1250	USD
CY2019Q3	ato	Minimum Continuing Investment For Direct Stock Purchase Plan MinimumContinuingInvestmentForDirectStockPurchasePlan	25	USD
CY2019Q3	ato	Annual Maximum Investment For Direct Stock Purchase Plan AnnualMaximumInvestmentForDirectStockPurchasePlan	100000	USD
CY2019Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	246470000	USD
CY2018Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	268090000	USD
CY2019Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	15899000	USD
CY2018Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	14795000	USD
CY2019Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	230571000	USD
CY2018Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	253295000	USD
CY2019Q3	us-gaap	Deferred Gas Cost DeferredGasCost	23766000	USD
CY2018Q3	us-gaap	Deferred Gas Cost DeferredGasCost	1927000	USD
CY2019Q3	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	38895000	USD
CY2018Q3	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	33233000	USD
CY2019Q3	us-gaap	Supplies Supplies	5916000	USD
CY2018Q3	us-gaap	Supplies Supplies	8106000	USD
CY2019Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	1586000	USD
CY2018Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	1369000	USD
CY2019Q3	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	2609000	USD
CY2018Q3	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	1420000	USD
CY2019Q3	us-gaap	Other Assets Current OtherAssetsCurrent	72772000	USD
CY2018Q3	us-gaap	Other Assets Current OtherAssetsCurrent	46055000	USD
CY2019Q3	ato	Public Utilities Property Plantand Equipment Storage PublicUtilitiesPropertyPlantandEquipmentStorage	431286000	USD
CY2018Q3	ato	Public Utilities Property Plantand Equipment Storage PublicUtilitiesPropertyPlantandEquipmentStorage	414857000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	3157316000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	2851423000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	9333011000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	8141733000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Common PublicUtilitiesPropertyPlantAndEquipmentCommon	799095000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Common PublicUtilitiesPropertyPlantAndEquipmentCommon	771355000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	38191000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	38280000	USD
CY2019Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	13758899000	USD
CY2018Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	12217648000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	421694000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	349725000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	14180593000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	12567373000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	2392924000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	2196226000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	11787669000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	10371147000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Amount Of Acquisition Adjustments1 PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1	-46700000	USD
CY2018Q3	us-gaap	Public Utilities Property Plant And Equipment Amount Of Acquisition Adjustments1 PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1	-55500000	USD
CY2018Q3	us-gaap	Goodwill Goodwill	730419000	USD
CY2019	us-gaap	Goodwill Other Increase Decrease GoodwillOtherIncreaseDecrease	-287000	USD
CY2019Q3	us-gaap	Goodwill Goodwill	730706000	USD
CY2019	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	300000	USD
CY2019Q3	us-gaap	Accounts Payable Current And Noncurrent AccountsPayableCurrentAndNoncurrent	176581000	USD
CY2018Q3	us-gaap	Accounts Payable Current And Noncurrent AccountsPayableCurrentAndNoncurrent	135159000	USD
CY2019Q3	ato	Accrued Gas Payable AccruedGasPayable	36817000	USD
CY2018Q3	ato	Accrued Gas Payable AccruedGasPayable	48721000	USD
CY2019Q3	us-gaap	Accrued Liabilities Current And Noncurrent AccruedLiabilitiesCurrentAndNoncurrent	51626000	USD
CY2018Q3	us-gaap	Accrued Liabilities Current And Noncurrent AccruedLiabilitiesCurrentAndNoncurrent	33403000	USD
CY2019Q3	us-gaap	Accounts Payable And Accrued Liabilities Current And Noncurrent AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	265024000	USD
CY2018Q3	us-gaap	Accounts Payable And Accrued Liabilities Current And Noncurrent AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	217283000	USD
CY2019Q3	us-gaap	Customer Deposits Current CustomerDepositsCurrent	54617000	USD
CY2018Q3	us-gaap	Customer Deposits Current CustomerDepositsCurrent	52648000	USD
CY2019Q3	us-gaap	Accrued Employee Benefits Current AccruedEmployeeBenefitsCurrent	55216000	USD
CY2018Q3	us-gaap	Accrued Employee Benefits Current AccruedEmployeeBenefitsCurrent	52101000	USD
CY2019Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	14112000	USD
CY2018Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	94705000	USD
CY2019Q3	us-gaap	Interest Payable Current InterestPayableCurrent	51381000	USD
CY2018Q3	us-gaap	Interest Payable Current InterestPayableCurrent	39486000	USD
CY2019Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	4552000	USD
CY2018Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	56734000	USD
CY2019Q3	us-gaap	Taxes Payable Current TaxesPayableCurrent	135597000	USD
CY2018Q3	us-gaap	Taxes Payable Current TaxesPayableCurrent	123457000	USD
CY2019Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	26197000	USD
CY2018Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	10475000	USD
CY2019Q3	ato	Costofservicereservecurrent Costofservicereservecurrent	4209000	USD
CY2018Q3	ato	Costofservicereservecurrent Costofservicereservecurrent	22508000	USD
CY2019Q3	ato	Regulatory Cost Of Removal Liability Current RegulatoryCostOfRemovalLiabilityCurrent	55721000	USD
CY2018Q3	ato	Regulatory Cost Of Removal Liability Current RegulatoryCostOfRemovalLiabilityCurrent	55770000	USD
CY2019Q3	ato	Regulatory Clause Revenues Over Recoveredcurrent RegulatoryClauseRevenuesOverRecoveredcurrent	52856000	USD
CY2018Q3	ato	Regulatory Clause Revenues Over Recoveredcurrent RegulatoryClauseRevenuesOverRecoveredcurrent	19918000	USD
CY2019Q3	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	21206000	USD
CY2018Q3	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	5225000	USD
CY2019Q3	ato	Other Liabilities Current Other OtherLiabilitiesCurrentOther	3837000	USD
CY2018Q3	ato	Other Liabilities Current Other OtherLiabilitiesCurrentOther	14041000	USD
CY2019Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	479501000	USD
CY2018Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	547068000	USD
CY2019Q3	us-gaap	Customer Advances For Construction CustomerAdvancesForConstruction	12566000	USD
CY2018Q3	us-gaap	Customer Advances For Construction CustomerAdvancesForConstruction	11010000	USD
CY2019Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	16120000	USD
CY2018Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	78599000	USD
CY2019Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	17054000	USD
CY2018Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	12887000	USD
CY2019Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	1249000	USD
CY2018Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	103000	USD
CY2019Q3	ato	Regulatory Clause Revenues Over Recoveredlongterm RegulatoryClauseRevenuesOverRecoveredlongterm	25545000	USD
CY2018Q3	ato	Regulatory Clause Revenues Over Recoveredlongterm RegulatoryClauseRevenuesOverRecoveredlongterm	15310000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	27716000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	26203000	USD
CY2019Q3	ato	Other Liabilities Noncurrent Other OtherLiabilitiesNoncurrentOther	20883000	USD
CY2018Q3	ato	Other Liabilities Noncurrent Other OtherLiabilitiesNoncurrentOther	13916000	USD
CY2019Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	121133000	USD
CY2018Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	158028000	USD
CY2019	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	11165000	USD
CY2018	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	0	USD
CY2017	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	0	USD
CY2019	ato	Performancebasedrateprogram Performancebasedrateprogram	6737000	USD
CY2018	ato	Performancebasedrateprogram Performancebasedrateprogram	6745000	USD
CY2017	ato	Performancebasedrateprogram Performancebasedrateprogram	9240000	USD
CY2019	ato	Pensionand Other Postretirement Non Service Cost PensionandOtherPostretirementNonServiceCost	3016000	USD
CY2018	ato	Pensionand Other Postretirement Non Service Cost PensionandOtherPostretirementNonServiceCost	-5770000	USD
CY2017	ato	Pensionand Other Postretirement Non Service Cost PensionandOtherPostretirementNonServiceCost	-8469000	USD
CY2019	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	4160000	USD
CY2018	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	1450000	USD
CY2017	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	1390000	USD
CY2019	ato	Charitable Contributions CharitableContributions	4771000	USD
CY2018	ato	Charitable Contributions CharitableContributions	6053000	USD
CY2017	ato	Charitable Contributions CharitableContributions	4413000	USD
CY2019	ato	Gainlossonassetsheldintrusts Gainlossonassetsheldintrusts	-1349000	USD
CY2018	ato	Gainlossonassetsheldintrusts Gainlossonassetsheldintrusts	0	USD
CY2017	ato	Gainlossonassetsheldintrusts Gainlossonassetsheldintrusts	0	USD
CY2019	ato	Miscellaneous Non Operating Income Expense MiscellaneousNonOperatingIncomeExpense	-11554000	USD
CY2018	ato	Miscellaneous Non Operating Income Expense MiscellaneousNonOperatingIncomeExpense	-6516000	USD
CY2017	ato	Miscellaneous Non Operating Income Expense MiscellaneousNonOperatingIncomeExpense	-9100000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	7404000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-10144000	USD
CY2017	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-11352000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	184852000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	169987000	USD
CY2017	us-gaap	Interest Paid Net InterestPaidNet	156668000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	11467000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	6102000	USD
CY2017	us-gaap	Income Taxes Paid IncomeTaxesPaid	5264000	USD
CY2019	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	149993	USD
CY2018	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	112211	USD
CY2017	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	116194	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	21017000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due Current CapitalLeasesFutureMinimumPaymentsDueCurrent	243000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	20416000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due In Two Years CapitalLeasesFutureMinimumPaymentsDueInTwoYears	248000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	19370000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due In Three Years CapitalLeasesFutureMinimumPaymentsDueInThreeYears	253000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	18071000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due In Four Years CapitalLeasesFutureMinimumPaymentsDueInFourYears	258000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	15718000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due In Five Years CapitalLeasesFutureMinimumPaymentsDueInFiveYears	263000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	105544000	USD
CY2019Q3	ato	Deferred Tax Assets Charitable Contributionand Other Tax Credit Carryforwards DeferredTaxAssetsCharitableContributionandOtherTaxCreditCarryforwards	8241000	USD
CY2018Q3	ato	Deferred Tax Assets Charitable Contributionand Other Tax Credit Carryforwards DeferredTaxAssetsCharitableContributionandOtherTaxCreditCarryforwards	6818000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due Thereafter CapitalLeasesFutureMinimumPaymentsDueThereafter	4343000	USD
CY2019Q3	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	200136000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Due CapitalLeasesFutureMinimumPaymentsDue	5608000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Interest Included In Payments CapitalLeasesFutureMinimumPaymentsInterestIncludedInPayments	3018000	USD
CY2019Q3	us-gaap	Capital Leases Future Minimum Payments Present Value Of Net Minimum Payments CapitalLeasesFutureMinimumPaymentsPresentValueOfNetMinimumPayments	2590000	USD
CY2019	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	40400000	USD
CY2018	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	33800000	USD
CY2017	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	32700000	USD
CY2019	ato	Self Insured Retention Expense SelfInsuredRetentionExpense	1000000.0	USD
CY2019	ato	Significant Purchase Commitment Amount SignificantPurchaseCommitmentAmount	50800000	USD
CY2018	ato	Significant Purchase Commitment Amount SignificantPurchaseCommitmentAmount	57200000	USD
CY2017	ato	Significant Purchase Commitment Amount SignificantPurchaseCommitmentAmount	49700000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-10099000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	8412000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	11075000	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	9022000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	113331000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	150556000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	197013000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	17160000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	15330000	USD
CY2017	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	15348000	USD
CY2019	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	-158782000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	138903000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	8080000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	221383000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	165701000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	169947000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	136565000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	149730000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	211433000	USD
CY2019	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	1460000	USD
CY2018	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	1745000	USD
CY2017	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	2584000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	20202000	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	19826000	USD
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	16100000	USD
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	-14085000	USD
CY2018	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	-1219000	USD
CY2017	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	0	USD
CY2019	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	-158782000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-2319000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	270000	USD
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-3566000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	138903000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	8080000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	221383000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.245
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2019Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	70929000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	72745000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	33918000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	27135000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	485133000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	461481000	USD
CY2018Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	5503000	USD
CY2017Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	8302000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	13186000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	13804000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	777108000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	751930000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1894000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1465000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	775214000	USD
CY2018Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	750465000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	2004516000	USD
CY2018Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	1859787000	USD
CY2019Q3	ato	Deferred Tax Liabilities Pension Liability DeferredTaxLiabilitiesPensionLiability	4384000	USD
CY2018Q3	ato	Deferred Tax Liabilities Pension Liability DeferredTaxLiabilitiesPensionLiability	6986000	USD
CY2019Q3	ato	Deferred Tax Liability Gas Cost Adjustments DeferredTaxLiabilityGasCostAdjustments	18072000	USD
CY2018Q3	ato	Deferred Tax Liability Gas Cost Adjustments DeferredTaxLiabilityGasCostAdjustments	-1005000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	48257000	USD
CY2018Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	38764000	USD
CY2019Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2075229000	USD
CY2018Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1904532000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1300015000	USD
CY2018Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1154067000	USD
CY2019Q3	ato	Deferred Tax Assets Deferred Credits DeferredTaxAssetsDeferredCredits	2582000	USD
CY2018Q3	ato	Deferred Tax Assets Deferred Credits DeferredTaxAssetsDeferredCredits	762000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Charitable Contribution Carryforwards DeferredTaxAssetsCharitableContributionCarryforwards	5500000	USD
CY2019Q3	ato	Deferred Tax Assets Operating Loss Carryforwards Domestic Impact State And Local DeferredTaxAssetsOperatingLossCarryforwardsDomesticImpactStateAndLocal	500000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	27700000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	26203000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	23719000	USD
CY2016Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	20298000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	923000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	22000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	366000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	2436000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	2462000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3787000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	27716000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	26203000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	23719000	USD
CY2019Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	5820000	USD
CY2018	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	2400000	USD
CY2017	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	1000000.0	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	58406000	USD
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.38
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.83
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.68
CY2019Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	21896000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	20700000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	15417000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	2200000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	1600000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	1100000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	7900000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	6100000	USD
CY2017Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	4500000	USD
CY2018	ato	Tax Cutsand Jobs Actof2017 Changein Tax Rate Income Tax Benefit TaxCutsandJobsActof2017ChangeinTaxRateIncomeTaxBenefit	158800000	USD
CY2019Q3	ato	Tax Cutsand Jobs Actof2017 Changein Tax Rate Regulatory Liability TaxCutsandJobsActof2017ChangeinTaxRateRegulatoryLiability	726300000	USD
CY2018Q3	ato	Tax Cutsand Jobs Actof2017 Changein Tax Rate Regulatory Liability TaxCutsandJobsActof2017ChangeinTaxRateRegulatoryLiability	744900000	USD
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2019Q3	ato	Regulatory Costof Service Liability RegulatoryCostofServiceLiability	5200000	USD
CY2018Q3	ato	Regulatory Costof Service Liability RegulatoryCostofServiceLiability	22500000	USD
CY2019Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	1586000	USD
CY2018Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	1369000	USD
CY2019Q3	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	225000	USD
CY2018Q3	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	250000	USD
CY2019Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	4552000	USD
CY2018Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	56734000	USD
CY2019Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	1249000	USD
CY2018Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	103000	USD
CY2019Q3	us-gaap	Derivative Assets Liabilities At Fair Value Net DerivativeAssetsLiabilitiesAtFairValueNet	-3990000	USD
CY2018Q3	us-gaap	Derivative Assets Liabilities At Fair Value Net DerivativeAssetsLiabilitiesAtFairValueNet	-55218000	USD
CY2019Q3	ato	Accumulated Other Comprehensive Income Loss Derivatives Qualifyingas Hedges Interest Rate Agreements Realized Gain Loss Netof Tax AccumulatedOtherComprehensiveIncomeLossDerivativesQualifyingasHedgesInterestRateAgreementsRealizedGainLossNetofTax	-114700000	USD
CY2019Q3	ato	Derivative Asset Netof Contract Netting DerivativeAssetNetofContractNetting	1811000	USD
CY2019Q3	ato	Derivative Liability Netof Contract Netting DerivativeLiabilityNetofContractNetting	5801000	USD
CY2018Q3	ato	Derivative Asset Netof Contract Netting DerivativeAssetNetofContractNetting	1619000	USD
CY2018Q3	ato	Derivative Liability Netof Contract Netting DerivativeLiabilityNetofContractNetting	56837000	USD
CY2019	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	3900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	44936000	USD
CY2019	ato	Other Comprehensive Income Unrealized Gain Loss On Interest Rate Agreements Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnInterestRateAgreementsArisingDuringPeriodNetOfTax	-25966000	USD
CY2018	ato	Other Comprehensive Income Unrealized Gain Loss On Interest Rate Agreements Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnInterestRateAgreementsArisingDuringPeriodNetOfTax	43184000	USD
CY2019	ato	Other Comprehensive Income Reclassification Adjustment On Interest Rate Agreements Included In Net Income Net Of Tax OtherComprehensiveIncomeReclassificationAdjustmentOnInterestRateAgreementsIncludedInNetIncomeNetOfTax	3022000	USD
CY2018	ato	Other Comprehensive Income Reclassification Adjustment On Interest Rate Agreements Included In Net Income Net Of Tax OtherComprehensiveIncomeReclassificationAdjustmentOnInterestRateAgreementsIncludedInNetIncomeNetOfTax	1752000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Derivatives Qualifying As Hedges Net Of Tax OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax	-22944000	USD
CY2019Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2019Q3	us-gaap	Derivative Assets DerivativeAssets	1811000	USD
CY2019Q3	ato	Debtandequitysecurities Debtandequitysecurities	101883000	USD
CY2019Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2019Q3	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	103694000	USD
CY2019Q3	us-gaap	Derivative Liability Fair Value Gross Asset And Right To Reclaim Cash Offset DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset	0	USD
CY2019Q3	us-gaap	Derivative Liabilities DerivativeLiabilities	5801000	USD
CY2018Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2018Q3	us-gaap	Derivative Assets DerivativeAssets	1619000	USD
CY2018Q3	ato	Debtandequitysecurities Debtandequitysecurities	99385000	USD
CY2018Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2018Q3	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	101004000	USD
CY2018Q3	us-gaap	Derivative Liability Fair Value Gross Asset And Right To Reclaim Cash Offset DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset	0	USD
CY2018Q3	us-gaap	Derivative Liabilities DerivativeLiabilities	56837000	USD
CY2019Q3	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	4216249000	USD
CY2019Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	3560000000	USD
CY2017	us-gaap	Change In Unrealized Gain Loss On Fair Value Hedging Instruments1 ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1	-9567000	USD
CY2017	us-gaap	Change In Unrealized Gain Loss On Hedged Item In Fair Value Hedge1 ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1	12858000	USD
CY2017	us-gaap	Gain Loss On Fair Value Hedges Recognized In Earnings GainLossOnFairValueHedgesRecognizedInEarnings	3291000	USD
CY2017	ato	Fair Value Hedge Basis Ineffectiveness FairValueHedgeBasisIneffectiveness	597000	USD
CY2017	ato	Fair Value Hedge Timing Ineffectiveness FairValueHedgeTimingIneffectiveness	-3888000	USD
CY2017	us-gaap	Gain Loss On Fair Value Hedges Recognized In Earnings GainLossOnFairValueHedgesRecognizedInEarnings	3291000	USD
CY2017	ato	Cash Flow Hedge Gain Loss Reclassifiedto Purchased Gas Cost Net CashFlowHedgeGainLossReclassifiedtoPurchasedGasCostNet	-2612000	USD
CY2017	us-gaap	Gain Loss On Cash Flow Hedge Ineffectiveness Net GainLossOnCashFlowHedgeIneffectivenessNet	111000	USD
CY2017	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	10579000	USD
CY2017	ato	Cash Flow Hedge Gain Loss Included In Cost Of Sales Net CashFlowHedgeGainLossIncludedInCostOfSalesNet	8078000	USD
CY2018Q4	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	877782000	USD
CY2019Q1	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	1094645000	USD
CY2019Q2	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	485738000	USD
CY2019Q3	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	443683000	USD
CY2018Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	236464000	USD
CY2019Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	297677000	USD
CY2019Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	122202000	USD
CY2019Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	89715000	USD
CY2018Q4	us-gaap	Net Income Loss NetIncomeLoss	157646000	USD
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.38
CY2018Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	270902000	USD
CY2018Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	124320000	USD
CY2018Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	90629000	USD
CY2017Q4	us-gaap	Net Income Loss NetIncomeLoss	314132000	USD
CY2018Q1	us-gaap	Net Income Loss NetIncomeLoss	178992000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	214888000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	80466000	USD
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.49
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.82
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.68
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.49
CY2017Q4	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	889192000	USD
CY2018Q1	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	1219409000	USD
CY2018Q2	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	562245000	USD
CY2018Q3	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	444700000	USD
CY2017Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	242083000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	71193000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	38747000	USD
CY2017Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.89
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.60
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.64
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.35
CY2017Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.89
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.60
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.64
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.35

Files In Submission

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$ATO
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2019 Q3 Form 10-K Financial Statement

#000073180219000037 Filed on November 12, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

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$ATO Atmos Energy Corp Stock $ato

2019 Q3 Form 10-K Financial Statement

#000073180219000037 Filed on November 12, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$ATO
Atmos Energy Corp Stock $ato