$ATO
Atmos Energy Corp Stock $ato

$ato Overview Financials Valuation SEC Filings Company Website

2020 Q3 Form 10-K Financial Statement

#000073180220000040 Filed on November 13, 2020

Income Statement

Concept	2020 Q3	2019 Q3	2019 Q2
Revenue	$474.9M	$443.7M	$485.7M
YoY Change	7.04%	-0.23%	-13.61%
Cost Of Revenue	$18.00M	$13.70M	$31.33M
YoY Change	31.39%	-68.21%	-76.07%
Gross Profit	$456.9M	$430.0M	$454.4M
YoY Change	6.26%	7.07%	5.34%
Gross Profit Margin	96.21%	96.92%	93.55%
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$111.7M	$101.0M	$97.70M
YoY Change	10.59%	8.95%	7.84%
% of Gross Profit	24.45%	23.49%	21.5%
Operating Expenses	$356.1M	$340.3M	$332.2M
YoY Change	4.64%	9.07%	7.72%
Operating Profit	$100.8M	$89.72M	$122.2M
YoY Change	12.41%	-1.01%	-1.7%
Interest Expense	-$15.50M	-$28.80M	$19.59M
YoY Change	-46.18%	17.55%	-16.09%
% of Operating Profit	-15.37%	-32.1%	16.03%
Other Income/Expense, Net	-$2.000M	$9.300M	$1.645M
YoY Change	-121.51%	-945.45%	-149.4%
Pretax Income	$83.40M	$70.20M	$104.3M
YoY Change	18.8%	9.52%	6.77%
Income Tax	$18.10M	$11.80M	$23.79M
% Of Pretax Income	21.7%	16.81%	22.82%
Net Earnings	$65.33M	$58.41M	$80.47M
YoY Change	11.86%	50.74%	13.03%
Net Earnings / Revenue	13.76%	13.16%	16.57%
Basic Earnings Per Share	$0.53	$0.49	$0.68
Diluted Earnings Per Share	$0.53	$0.49	$0.68
COMMON SHARES
Basic Shares Outstanding	123.4M shares	118.2M shares	118.1M shares
Diluted Shares Outstanding			118.4M shares

Balance Sheet

Concept	2020 Q3	2019 Q3	2019 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments	$124.8M	$25.00M	$46.00M
YoY Change	399.04%	78.57%	119.05%
Cash & Equivalents	$20.81M	$24.55M	$46.16M
Short-Term Investments	$104.0M
Other Short-Term Assets	$107.9M	$72.77M	$65.92M
YoY Change	48.28%	58.01%	25.88%
Inventory	$112.0M	$130.0M	$106.0M
Prepaid Expenses	$40.34M	$38.90M
Receivables	$230.6M	$230.6M	$285.4M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$471.3M	$458.0M	$503.5M
YoY Change	2.89%	-4.35%	11.19%
LONG-TERM ASSETS
Property, Plant & Equipment	$13.58B	$11.79B	$11.34B
YoY Change	15.22%	13.66%	12.6%
Goodwill	$731.3M	$730.7M	$730.4M
YoY Change	0.08%	0.04%	0.04%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$801.2M	$391.2M	$306.5M
YoY Change	104.79%	33.06%	21.27%
Total Long-Term Assets	$14.89B	$12.91B	$12.38B
YoY Change	15.32%	13.29%	11.97%
TOTAL ASSETS
Total Short-Term Assets	$471.3M	$458.0M	$503.5M
Total Long-Term Assets	$14.89B	$12.91B	$12.38B
Total Assets	$15.36B	$13.37B	$12.88B
YoY Change	14.9%	12.57%	11.94%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$236.0M	$265.0M	$207.0M
YoY Change	-10.94%	22.12%	4.55%
Accrued Expenses	$36.00M
YoY Change
Deferred Revenue	$56.49M	$54.62M
YoY Change	3.42%
Short-Term Debt	$0.00	$464.9M	$74.94M
YoY Change	-100.0%	-19.25%	-69.38%
Long-Term Debt Due	$0.00	$0.00	$125.0M
YoY Change		-100.0%	-72.22%
Total Short-Term Liabilities	$782.4M	$1.209B	$901.4M
YoY Change	-35.31%	-36.85%	-38.51%
LONG-TERM LIABILITIES
Long-Term Debt	$4.532B	$3.529B	$3.529B
YoY Change	28.41%	41.54%	34.79%
Other Long-Term Liabilities	$642.1M	$400.2M	$175.9M
YoY Change	60.45%	153.26%	135.36%
Total Long-Term Liabilities	$642.1M	$3.930B	$3.705B
YoY Change	-83.66%	48.19%	37.58%
TOTAL LIABILITIES
Total Short-Term Liabilities	$782.4M	$1.209B	$901.4M
Total Long-Term Liabilities	$642.1M	$3.930B	$3.705B
Total Liabilities	$1.425B	$5.139B	$4.606B
YoY Change	-72.28%	12.53%	10.76%
SHAREHOLDERS EQUITY
Retained Earnings	$2.471B	$2.152B	$2.157B
YoY Change	14.82%	14.58%	15.28%
Common Stock	$4.378B	$3.713B	$3.600B
YoY Change	17.91%	24.78%	21.44%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$6.791B	$5.750B	$5.642B
YoY Change
Total Liabilities & Shareholders Equity	$15.36B	$13.37B	$12.88B
YoY Change	14.9%	12.57%	11.94%

Cashflow Statement

Concept	2020 Q3	2019 Q3	2019 Q2
OPERATING ACTIVITIES
Net Income	$65.33M	$58.41M	$80.47M
YoY Change	11.86%	50.74%	13.03%
Depreciation, Depletion And Amortization	$111.7M	$101.0M	$97.70M
YoY Change	10.59%	8.95%	7.84%
Cash From Operating Activities	$142.5M	$159.9M	$248.1M
YoY Change	-10.88%	78.86%	-12.61%
INVESTING ACTIVITIES
Capital Expenditures	-$530.0M	-$494.3M	-$421.6M
YoY Change	7.22%	30.39%	6.87%
Acquisitions
YoY Change
Other Investing Activities	$4.800M	$6.000M	-$5.400M
YoY Change	-20.0%	114.29%	17.39%
Cash From Investing Activities	-$525.2M	-$488.3M	-$427.0M
YoY Change	7.56%	29.73%	6.99%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	195.5M	306.8M	116.7M
YoY Change	-36.28%	9.61%	79.54%
NET CHANGE
Cash From Operating Activities	142.5M	159.9M	248.1M
Cash From Investing Activities	-525.2M	-488.3M	-427.0M
Cash From Financing Activities	195.5M	306.8M	116.7M
Net Change In Cash	-187.2M	-21.60M	-62.20M
YoY Change	766.67%	204.23%	23.9%
FREE CASH FLOW
Cash From Operating Activities	$142.5M	$159.9M	$248.1M
Capital Expenditures	-$530.0M	-$494.3M	-$421.6M
Free Cash Flow	$672.5M	$654.2M	$669.7M
YoY Change	2.8%	39.64%	-1.28%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2019Q3	ato	Derivative Cash Collateral DerivativeCashCollateral	0	USD
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--09-30
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0000731802
CY2020Q4	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201602Member
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
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	2.30
CY2019Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.005
CY2020Q3	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.005
CY2019Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2020Q3	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	200000000	shares
CY2019Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	119338925	shares
CY2020Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	125882477	shares
CY2019Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	119338925	shares
CY2020Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	125882477	shares
CY2020Q3	us-gaap	Finance Lease Liability Current Statement Of Financial Position Extensible List FinanceLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
CY2020Q3	us-gaap	Finance Lease Liability Noncurrent Statement Of Financial Position Extensible List FinanceLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList	us-gaap:LongTermDebtAndCapitalLeaseObligations
CY2020Q3	us-gaap	Finance Lease Right Of Use Asset Statement Of Financial Position Extensible List FinanceLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	us-gaap:PublicUtilitiesPropertyPlantAndEquipmentNet
CY2020Q3	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	us-gaap:OtherLiabilitiesCurrent
CY2020Q3	us-gaap	Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList	us-gaap:OtherLiabilitiesNoncurrent
CY2020Q3	us-gaap	Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	us-gaap:OtherAssetsNoncurrent
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTaxParent	13017000	USD
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CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTaxParent	17198000	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
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	32000	USD
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-09-30
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	1-10042
CY2020	dei	Entity Registrant Name EntityRegistrantName	Atmos Energy Corp
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	TX
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	75-1743247
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	1800 Three Lincoln Centre
CY2020	dei	Entity Address Address Line2 EntityAddressAddressLine2	5430 LBJ Freeway
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Dallas
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	TX
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	75240
CY2020	dei	City Area Code CityAreaCode	972
CY2020	dei	Local Phone Number LocalPhoneNumber	934-9227
CY2020	dei	Security12b Title Security12bTitle	Common stock
CY2020	dei	Trading Symbol TradingSymbol	ATO
CY2020	dei	Security Exchange Name SecurityExchangeName	NYSE
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
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CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
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CY2020Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	15539166000	USD
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CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	218000	USD
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CY2018	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	395092000	USD
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CY2018	us-gaap	Increase Decrease In Other Current Liabilities IncreaseDecreaseInOtherCurrentLiabilities	74707000	USD
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CY2018	us-gaap	Increase Decrease In Other Noncurrent Liabilities IncreaseDecreaseInOtherNoncurrentLiabilities	31923000	USD
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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
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CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1693477000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1467591000	USD
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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
CY2020	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	50517000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	29153000	USD
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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
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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
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CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-8601000	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-9350000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1925518000	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
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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
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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
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CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	694103000	USD
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CY2020	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	19548000	USD
CY2019	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	19323000	USD
CY2018	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	19563000	USD
CY2020	us-gaap	Payments For Proceeds From Hedge Financing Activities PaymentsForProceedsFromHedgeFinancingActivities	4426000	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
CY2020	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	575000000	USD
CY2018	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	0	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	282444000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	245717000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	214906000	USD
CY2020	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	7738000	USD
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	11254000	USD
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
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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
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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
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CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	10779000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-12638000	USD
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	24550000	USD
CY2018Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	13771000	USD
CY2017Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	26409000	USD
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	20808000	USD
CY2019Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	24550000	USD
CY2018Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	13771000	USD
CY2020	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;"> </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 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.
CY2020	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;"> </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>
CY2020Q3	ato	Number Of Customers Regulated Distribution NumberOfCustomersRegulatedDistribution	3000000000000	customer
CY2020Q3	ato	Number Of Divisions Regulated Distribution NumberOfDivisionsRegulatedDistribution	6	regulated_distribution_division
CY2020	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>
CY2020Q3	us-gaap	Regulatory Assets RegulatoryAssets	414641000	USD
CY2019Q3	us-gaap	Regulatory Assets RegulatoryAssets	284547000	USD
CY2020Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	1367013000	USD
CY2019Q3	us-gaap	Regulatory Liabilities RegulatoryLiabilities	1386126000	USD
CY2019	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	7643000	USD
CY2020	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	8436000	USD
CY2018	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Interest PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest	6810000	USD
CY2020	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	23493000	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
CY2020	us-gaap	Public Utilities Allowance For Funds Used During Construction Additions PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	31929000	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
CY2020	us-gaap	Public Utilities Property Plant And Equipment Disclosure Of Composite Depreciation Rate For Plants In Service PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService	0.030
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
CY2020Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	20300000	USD
CY2019Q3	us-gaap	Asset Retirement Obligation AssetRetirementObligation	17100000	USD
CY2020Q3	ato	Asset Retirement Costs In Property Plant And Equipment AssetRetirementCostsInPropertyPlantAndEquipment	14400000	USD
CY2019Q3	ato	Asset Retirement Costs In Property Plant And Equipment AssetRetirementCostsInPropertyPlantAndEquipment	11300000	USD
CY2020	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 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 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 currently manage this risk through the use of forward starting interest rate swaps to fix the Treasury yield component of the interest cost associated with anticipated financings. We designate these financial instruments as cash flow hedges at the time the agreements are executed. Unrealized gains and losses associated with the instruments are recorded as a component of accumulated other comprehensive income (loss). When the instruments settle, the realized gain or loss is recorded as a component of accumulated other comprehensive income (loss) and recognized as a component of interest charges over the life of the related financing arrangement. As of </span><span style="font-family:inherit;font-size:10pt;">September 30, 2020</span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;">2019</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>
CY2020Q3	ato	Derivative Cash Collateral DerivativeCashCollateral	0	USD
CY2020	us-gaap	Revenues Revenues	2821137000	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020Q3	us-gaap	Number Of States In Which Entity Operates NumberOfStatesInWhichEntityOperates	8	state
CY2020	us-gaap	Revenues Revenues	2821137000	USD
CY2020	us-gaap	Cost Of Revenue CostOfRevenue	658854000	USD
CY2020	us-gaap	Other Selling General And Administrative Expense OtherSellingGeneralAndAdministrativeExpense	629601000	USD
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	429828000	USD
CY2020	us-gaap	Taxes Other TaxesOther	278755000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	824099000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	7171000	USD
CY2020	us-gaap	Interest Expense InterestExpense	84474000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	746796000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	145353000	USD
CY2020	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	601443000	USD
CY2020	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1935676000	USD
CY2019	us-gaap	Revenues Revenues	2901848000	USD
CY2019	us-gaap	Revenues Revenues	2901848000	USD
CY2019	us-gaap	Cost Of Revenue CostOfRevenue	858837000	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	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	511406000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1693477000	USD
CY2018	us-gaap	Revenues Revenues	3115546000	USD
CY2018	us-gaap	Revenues Revenues	3115546000	USD
CY2018	us-gaap	Cost Of Revenue CostOfRevenue	1167848000	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	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	603064000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	1467591000	USD
CY2020	us-gaap	Regulated Operating Revenue RegulatedOperatingRevenue	2821137000	USD
CY2019	us-gaap	Regulated Operating Revenue RegulatedOperatingRevenue	2901848000	USD
CY2018	us-gaap	Regulated Operating Revenue RegulatedOperatingRevenue	3115546000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	13355347000	USD
CY2020Q3	us-gaap	Assets Assets	15359032000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	11787669000	USD
CY2019Q3	us-gaap	Assets Assets	13367619000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	601443000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	511406000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	603064000	USD
CY2020	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	444000	USD
CY2019	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	416000	USD
CY2018	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	580000	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	600999000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	510990000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	602484000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	122788000	shares
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
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.89
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.36
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.43
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	600999000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	510990000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	602484000	USD
CY2020	us-gaap	Amount Of Dilutive Securities Stock Options And Restrictive Stock Units AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnits	0	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
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	600999000	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
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	122788000	shares
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
CY2020	us-gaap	Incremental Common Shares Attributable To Equity Forward Agreements IncrementalCommonSharesAttributableToEquityForwardAgreements	84000	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
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	122872000	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
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.89
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.35
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.43
CY2020Q3	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P19Y1M6D
CY2020Q3	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P10Y7M6D
CY2020Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	227146000	USD
CY2020Q3	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.080
CY2020Q3	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.029
CY2020	ato	Finance Lease Cost FinanceLeaseCost	622000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	40887000	USD
CY2020	us-gaap	Lease Cost LeaseCost	41509000	USD
CY2020Q3	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	8480000	USD
CY2020Q3	ato	Right Of Use Asset Finance Leaseand Operating Lease RightOfUseAssetFinanceLeaseandOperatingLease	235626000	USD
CY2020Q3	us-gaap	Finance Lease Liability Current FinanceLeaseLiabilityCurrent	165000	USD
CY2020Q3	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	35716000	USD
CY2020Q3	us-gaap	Finance Lease Liability Noncurrent FinanceLeaseLiabilityNoncurrent	8466000	USD
CY2020Q3	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	201071000	USD
CY2020Q3	ato	Lease Liability LeaseLiability	245418000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	37758000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	6083000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	34169000	USD
CY2020Q3	ato	Lessee Liability Payments Due Next Rolling Twelve Months LesseeLiabilityPaymentsDueNextRollingTwelveMonths	40790000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due In Next Rolling Twelve Months FinanceLeaseLiabilityPaymentsDueInNextRollingTwelveMonths	741000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due Next Rolling Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextRollingTwelveMonths	40049000	USD
CY2020Q3	ato	Lessee Liability Payments Due Next Rolling Two Years LesseeLiabilityPaymentsDueNextRollingTwoYears	38423000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due In Rolling Year Two FinanceLeaseLiabilityPaymentsDueInRollingYearTwo	751000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Two LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearTwo	37672000	USD
CY2020Q3	ato	Lessee Liability Payments Due Next Rolling Three Years LesseeLiabilityPaymentsDueNextRollingThreeYears	33266000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due In Rolling Year Three FinanceLeaseLiabilityPaymentsDueInRollingYearThree	762000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Three LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearThree	32504000	USD
CY2020Q3	ato	Lessee Liability Payments Due Next Rolling Four Years LesseeLiabilityPaymentsDueNextRollingFourYears	25464000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due In Rolling Year Four FinanceLeaseLiabilityPaymentsDueInRollingYearFour	773000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Four LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFour	24691000	USD
CY2020Q3	ato	Lessee Liability Payments Due Next Rolling Five Years LesseeLiabilityPaymentsDueNextRollingFiveYears	17666000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due In Rolling Year Five FinanceLeaseLiabilityPaymentsDueInRollingYearFive	784000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due In Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueInRollingYearFive	16882000	USD
CY2020Q3	ato	Lessee Liability Payments Due After Rolling Five Years LesseeLiabilityPaymentsDueAfterRollingFiveYears	139049000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due In Rolling After Year Five FinanceLeaseLiabilityPaymentsDueInRollingAfterYearFive	12666000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due After Rolling Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterRollingYearFive	126383000	USD
CY2020Q3	ato	Lease Liability Lease Payments LeaseLiabilityLeasePayments	294658000	USD
CY2020Q3	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	16477000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	278181000	USD
CY2020Q3	ato	Lease Liability Imputed Interest LeaseLiabilityImputedInterest	49240000	USD
CY2020Q3	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	7846000	USD
CY2020Q3	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	41394000	USD
CY2020Q3	ato	Lease Liability LeaseLiability	245418000	USD
CY2020Q3	us-gaap	Finance Lease Liability FinanceLeaseLiability	8631000	USD
CY2020Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	236787000	USD
CY2020Q3	ato	Lease Liability Current LeaseLiabilityCurrent	35881000	USD
CY2020Q3	us-gaap	Finance Lease Liability Current FinanceLeaseLiabilityCurrent	165000	USD
CY2020Q3	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	35716000	USD
CY2020Q3	ato	Lease Liability Noncurrent LeaseLiabilityNoncurrent	209537000	USD
CY2020Q3	us-gaap	Finance Lease Liability Noncurrent FinanceLeaseLiabilityNoncurrent	8466000	USD
CY2020Q3	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	201071000	USD
CY2020Q3	ato	Lease Liability LeaseLiability	245418000	USD
CY2020Q3	us-gaap	Finance Lease Liability FinanceLeaseLiability	8631000	USD
CY2020Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	236787000	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	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
CY2020Q3	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
CY2020Q3	us-gaap	Finance Lease Liability FinanceLeaseLiability	8631000	USD
CY2019Q3	us-gaap	Finance Lease Liability FinanceLeaseLiability	0	USD
CY2020Q3	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	4568631000	USD
CY2019Q3	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	3560000000	USD
CY2020Q3	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	583000	USD
CY2019Q3	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	193000	USD
CY2020Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	36104000	USD
CY2019Q3	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	30355000	USD
CY2020Q3	us-gaap	Long Term Debt And Capital Lease Obligations Current LongTermDebtAndCapitalLeaseObligationsCurrent	165000	USD
CY2019Q3	us-gaap	Long Term Debt And Capital Lease Obligations Current LongTermDebtAndCapitalLeaseObligationsCurrent	0	USD
CY2020Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	4531779000	USD
CY2019Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	3529452000	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	200000000	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	0	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	0	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	10000000	USD
CY2020Q3	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	4350000000	USD
CY2020Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	4560000000	USD
CY2020Q3	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	2200000000	USD
CY2020	us-gaap	Public Utilities Approved Debt Capital Structure Percentage PublicUtilitiesApprovedDebtCapitalStructurePercentage	0.70
CY2020	ato	Public Utilities Actual Debt Capital Structure Percentage PublicUtilitiesActualDebtCapitalStructurePercentage	0.42
CY2020Q3	us-gaap	Forward Contract Indexed To Issuers Equity Settlement Alternatives Shares At Fair Value ForwardContractIndexedToIssuersEquitySettlementAlternativesSharesAtFairValue	3335995	shares
CY2020Q3	us-gaap	Forward Contract Indexed To Issuers Equity Settlement Alternatives Cash At Fair Value ForwardContractIndexedToIssuersEquitySettlementAlternativesCashAtFairValue	345206000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	53349000	USD
CY2020	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-3645000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	56994000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-25747000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-3021000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-22726000	USD
CY2020	us-gaap	Remaining Recovery Period Of Regulatory Assets For Which No Return On Investment During Recovery Period Is Provided1 RemainingRecoveryPeriodOfRegulatoryAssetsForWhichNoReturnOnInvestmentDuringRecoveryPeriodIsProvided1	P15Y
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	21100000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23900000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	23900000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	11600000	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
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	11200000	shares
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	1300000	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period1 ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1	P3Y
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period1 ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1	P3Y
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
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	199985	shares
CY2020	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	102.34
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
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	242975	shares
CY2020	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	85.66
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
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	16803	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	96.87
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
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	443279	shares
CY2020Q3	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	99.28
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
CY2020Q3	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	13000000.0	USD
CY2020	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y6M
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Total Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue	20700000	USD
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
CY2020Q3	ato	Minimum Initial Investment For Direct Stock Purchase Plan MinimumInitialInvestmentForDirectStockPurchasePlan	1250	USD
CY2020Q3	ato	Minimum Continuing Investment For Direct Stock Purchase Plan MinimumContinuingInvestmentForDirectStockPurchasePlan	25	USD
CY2020Q3	ato	Annual Maximum Investment For Direct Stock Purchase Plan AnnualMaximumInvestmentForDirectStockPurchasePlan	100000	USD
CY2020Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	260544000	USD
CY2019Q3	us-gaap	Accounts Receivable Gross Current AccountsReceivableGrossCurrent	246470000	USD
CY2020Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	29949000	USD
CY2019Q3	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	15899000	USD
CY2020Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	230595000	USD
CY2019Q3	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	230571000	USD
CY2020Q3	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	40340000	USD
CY2019Q3	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	38895000	USD
CY2020Q3	us-gaap	Supplies Supplies	6829000	USD
CY2019Q3	us-gaap	Supplies Supplies	5916000	USD
CY2020Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	5687000	USD
CY2020Q3	us-gaap	Deferred Gas Cost DeferredGasCost	40593000	USD
CY2019Q3	us-gaap	Deferred Gas Cost DeferredGasCost	23766000	USD
CY2019Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	1586000	USD
CY2020Q3	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	14456000	USD
CY2019Q3	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	2609000	USD
CY2020Q3	us-gaap	Other Assets Current OtherAssetsCurrent	107905000	USD
CY2019Q3	us-gaap	Other Assets Current OtherAssetsCurrent	72772000	USD
CY2020Q3	ato	Public Utilities Property Plantand Equipment Storage PublicUtilitiesPropertyPlantandEquipmentStorage	530985000	USD
CY2019Q3	ato	Public Utilities Property Plantand Equipment Storage PublicUtilitiesPropertyPlantandEquipmentStorage	431286000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	3459765000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Transmission PublicUtilitiesPropertyPlantAndEquipmentTransmission	3157316000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	10680495000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Distribution PublicUtilitiesPropertyPlantAndEquipmentDistribution	9333011000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Common PublicUtilitiesPropertyPlantAndEquipmentCommon	829624000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Common PublicUtilitiesPropertyPlantAndEquipmentCommon	799095000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	38297000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Other Property Plant And Equipment PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	38191000	USD
CY2020Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	15539166000	USD
CY2019Q3	ato	Public Utilities Property Plantand Equipment Plantin Service Excluding Construction Workin Progress PublicUtilitiesPropertyPlantandEquipmentPlantinServiceExcludingConstructionWorkinProgress	13758899000	USD
CY2019Q3	ato	Accrued Gas Payable AccruedGasPayable	36817000	USD
CY2020Q3	us-gaap	Accrued Liabilities Current And Noncurrent AccruedLiabilitiesCurrentAndNoncurrent	52646000	USD
CY2019Q3	us-gaap	Accrued Liabilities Current And Noncurrent AccruedLiabilitiesCurrentAndNoncurrent	51626000	USD
CY2020Q3	us-gaap	Accounts Payable And Accrued Liabilities Current And Noncurrent AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	235775000	USD
CY2019Q3	us-gaap	Accounts Payable And Accrued Liabilities Current And Noncurrent AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	265024000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	418055000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Construction Work In Progress PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	421694000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	15957221000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Plant In Service PublicUtilitiesPropertyPlantAndEquipmentPlantInService	14180593000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	2601874000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Accumulated Depreciation PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	2392924000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	13355347000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Net PublicUtilitiesPropertyPlantAndEquipmentNet	11787669000	USD
CY2020Q3	us-gaap	Public Utilities Property Plant And Equipment Amount Of Acquisition Adjustments1 PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1	-37800000	USD
CY2019Q3	us-gaap	Public Utilities Property Plant And Equipment Amount Of Acquisition Adjustments1 PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1	-46700000	USD
CY2019Q3	us-gaap	Goodwill Goodwill	730706000	USD
CY2020	us-gaap	Goodwill Other Increase Decrease GoodwillOtherIncreaseDecrease	-551000	USD
CY2020Q3	us-gaap	Goodwill Goodwill	731257000	USD
CY2020	us-gaap	Goodwill Period Increase Decrease GoodwillPeriodIncreaseDecrease	600000	USD
CY2020Q3	us-gaap	Accounts Payable Current And Noncurrent AccountsPayableCurrentAndNoncurrent	141075000	USD
CY2019Q3	us-gaap	Accounts Payable Current And Noncurrent AccountsPayableCurrentAndNoncurrent	176581000	USD
CY2020Q3	ato	Accrued Gas Payable AccruedGasPayable	42054000	USD
CY2020Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	56485000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	54617000	USD
CY2020Q3	us-gaap	Accrued Employee Benefits Current AccruedEmployeeBenefitsCurrent	57057000	USD
CY2019Q3	us-gaap	Accrued Employee Benefits Current AccruedEmployeeBenefitsCurrent	55216000	USD
CY2020Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	19985000	USD
CY2019Q3	us-gaap	Refundable Gas Costs RefundableGasCosts	14112000	USD
CY2020Q3	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	35716000	USD
CY2020Q3	us-gaap	Interest Payable Current InterestPayableCurrent	53554000	USD
CY2019Q3	us-gaap	Interest Payable Current InterestPayableCurrent	51381000	USD
CY2020Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	2015000	USD
CY2019Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	4552000	USD
CY2020Q3	us-gaap	Taxes Payable Current TaxesPayableCurrent	148292000	USD
CY2019Q3	us-gaap	Taxes Payable Current TaxesPayableCurrent	135597000	USD
CY2020Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	29609000	USD
CY2019Q3	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	26197000	USD
CY2020Q3	ato	Costofservicereservecurrent Costofservicereservecurrent	1716000	USD
CY2019Q3	ato	Costofservicereservecurrent Costofservicereservecurrent	4209000	USD
CY2020Q3	ato	Regulatory Cost Of Removal Liability Current RegulatoryCostOfRemovalLiabilityCurrent	73908000	USD
CY2019Q3	ato	Regulatory Cost Of Removal Liability Current RegulatoryCostOfRemovalLiabilityCurrent	55721000	USD
CY2020Q3	ato	Regulatory Clause Revenues Over Recoveredcurrent RegulatoryClauseRevenuesOverRecoveredcurrent	43893000	USD
CY2019Q3	ato	Regulatory Clause Revenues Over Recoveredcurrent RegulatoryClauseRevenuesOverRecoveredcurrent	52856000	USD
CY2020Q3	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	20887000	USD
CY2019Q3	us-gaap	Regulatory Liability Current RegulatoryLiabilityCurrent	21206000	USD
CY2020Q3	ato	Other Liabilities Current Other OtherLiabilitiesCurrentOther	3344000	USD
CY2019Q3	ato	Other Liabilities Current Other OtherLiabilitiesCurrentOther	3837000	USD
CY2020Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	546461000	USD
CY2019Q3	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	479501000	USD
CY2019	ato	Performancebasedrateprogram Performancebasedrateprogram	6737000	USD
CY2018	ato	Performancebasedrateprogram Performancebasedrateprogram	6745000	USD
CY2020	ato	Pensionand Other Postretirement Non Service Cost PensionandOtherPostretirementNonServiceCost	-3189000	USD
CY2019	ato	Pensionand Other Postretirement Non Service Cost PensionandOtherPostretirementNonServiceCost	3016000	USD
CY2018	ato	Pensionand Other Postretirement Non Service Cost PensionandOtherPostretirementNonServiceCost	-5770000	USD
CY2020	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	2932000	USD
CY2019	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	4160000	USD
CY2020Q3	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Current And Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent	337303000	USD
CY2019Q3	us-gaap	Pension And Other Postretirement And Postemployment Benefit Plans Liabilities Current And Noncurrent PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesCurrentAndNoncurrent	279083000	USD
CY2020Q3	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	201071000	USD
CY2020Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	10060000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	12566000	USD
CY2020Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	17838000	USD
CY2019Q3	us-gaap	Regulatory Liability Noncurrent RegulatoryLiabilityNoncurrent	16120000	USD
CY2020Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	20348000	USD
CY2019Q3	us-gaap	Asset Retirement Obligations Noncurrent AssetRetirementObligationsNoncurrent	17054000	USD
CY2020Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	0	USD
CY2019Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	1249000	USD
CY2020Q3	ato	Regulatory Clause Revenues Over Recoveredlongterm RegulatoryClauseRevenuesOverRecoveredlongterm	13486000	USD
CY2019Q3	ato	Regulatory Clause Revenues Over Recoveredlongterm RegulatoryClauseRevenuesOverRecoveredlongterm	25545000	USD
CY2020Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	30921000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	27716000	USD
CY2020Q3	ato	Other Liabilities Noncurrent Other OtherLiabilitiesNoncurrentOther	11101000	USD
CY2019Q3	ato	Other Liabilities Noncurrent Other OtherLiabilitiesNoncurrentOther	20883000	USD
CY2020Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	642128000	USD
CY2019Q3	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	400216000	USD
CY2020	us-gaap	Public Utilities Allowance For Funds Used During Construction Capitalized Cost Of Equity PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	23493000	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
CY2020	ato	Performancebasedrateprogram Performancebasedrateprogram	6771000	USD
CY2018	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	1450000	USD
CY2020	ato	Charitable Contributions CharitableContributions	11728000	USD
CY2019	ato	Charitable Contributions CharitableContributions	4771000	USD
CY2018	ato	Charitable Contributions CharitableContributions	6053000	USD
CY2020	ato	Miscellaneous Non Operating Income Expense MiscellaneousNonOperatingIncomeExpense	-11108000	USD
CY2019	ato	Miscellaneous Non Operating Income Expense MiscellaneousNonOperatingIncomeExpense	-12903000	USD
CY2018	ato	Miscellaneous Non Operating Income Expense MiscellaneousNonOperatingIncomeExpense	-6516000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	7171000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	7404000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-10144000	USD
CY2020	us-gaap	Interest Paid InterestPaid	194993000	USD
CY2019	us-gaap	Interest Paid InterestPaid	184852000	USD
CY2018	us-gaap	Interest Paid InterestPaid	169987000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-3071000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	11467000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	6102000	USD
CY2020	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	113365000	USD
CY2019	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	149993000	USD
CY2018	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	112211000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	82300000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	91300000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	106800000	USD
CY2020	ato	Self Insured Retention Expense SelfInsuredRetentionExpense	1000000.0	USD
CY2020	ato	Significant Purchase Commitment Amount SignificantPurchaseCommitmentAmount	58500000	USD
CY2019	ato	Significant Purchase Commitment Amount SignificantPurchaseCommitmentAmount	50800000	USD
CY2018	ato	Significant Purchase Commitment Amount SignificantPurchaseCommitmentAmount	57200000	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
CY2020	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-20962000	USD
CY2020	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	0	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	0	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	-10099000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	14193000	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
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	143039000	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
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-11879000	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
CY2020	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	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
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	145353000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	138903000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	8080000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-21000000.0	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	156827000	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
CY2020	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	1419000	USD
CY2019	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	1460000	USD
CY2018	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	1745000	USD
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	22791000	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
CY2020	us-gaap	Income Tax Reconciliation Nondeductible Expense Amortization IncomeTaxReconciliationNondeductibleExpenseAmortization	-16125000	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
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	4241000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-2319000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	270000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	145353000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	138903000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	8080000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.245
CY2020Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	66991000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Postretirement Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPostretirementBenefits	70929000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	16719000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	33918000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	476507000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	485133000	USD
CY2020Q3	ato	Deferred Tax Assets Charitable Contributionand Other Tax Credit Carryforwards DeferredTaxAssetsCharitableContributionandOtherTaxCreditCarryforwards	8712000	USD
CY2019Q3	ato	Deferred Tax Assets Charitable Contributionand Other Tax Credit Carryforwards DeferredTaxAssetsCharitableContributionandOtherTaxCreditCarryforwards	8241000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	161565000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Regulatory Assets And Liabilities DeferredTaxAssetsRegulatoryAssetsAndLiabilities	165701000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	73542000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	13186000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	804036000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	777108000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1102000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	1894000	USD
CY2020Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	802934000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	775214000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	2138966000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	2004516000	USD
CY2020Q3	ato	Deferred Tax Liabilities Pension Liability DeferredTaxLiabilitiesPensionLiability	484000	USD
CY2019Q3	ato	Deferred Tax Liabilities Pension Liability DeferredTaxLiabilitiesPensionLiability	4384000	USD
CY2020Q3	ato	Deferred Tax Liability Gas Cost Adjustments DeferredTaxLiabilityGasCostAdjustments	23209000	USD
CY2019Q3	ato	Deferred Tax Liability Gas Cost Adjustments DeferredTaxLiabilityGasCostAdjustments	18072000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	96844000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	48257000	USD
CY2020Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2259503000	USD
CY2019Q3	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	2075229000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1456569000	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	1300015000	USD
CY2019Q3	ato	Deferred Tax Assets Deferred Credits DeferredTaxAssetsDeferredCredits	2582000	USD
CY2020Q3	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Goodwill DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill	129000000.0	USD
CY2019Q3	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Goodwill DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill	131000000.0	USD
CY2020Q3	us-gaap	Deferred Tax Assets Charitable Contribution Carryforwards DeferredTaxAssetsCharitableContributionCarryforwards	6900000	USD
CY2020Q3	ato	Deferred Tax Assets Operating Loss Carryforwards Domestic Impact State And Local DeferredTaxAssetsOperatingLossCarryforwardsDomesticImpactStateAndLocal	500000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	30900000	USD
CY2020Q3	ato	Deferred Tax Assets Deferred Credits DeferredTaxAssetsDeferredCredits	2537000	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
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	26000	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
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	3231000	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
CY2020Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	30921000	USD
CY2019Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	27716000	USD
CY2018Q3	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	26203000	USD
CY2020Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	6493000	USD
CY2019Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	5820000	USD
CY2018Q3	ato	Unrecognized Tax Benefits Deferred Federaland State Income Tax Benefits UnrecognizedTaxBenefitsDeferredFederalandStateIncomeTaxBenefits	5503000	USD
CY2020Q3	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	24428000	USD
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
CY2020	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	700000	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
CY2020Q3	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	8200000	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
CY2020Q2	ato	Deferred Tax Liabilities Reduction Following Remeasurement DeferredTaxLiabilitiesReductionFollowingRemeasurement	32500000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-21000000.0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Income Tax Expense Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateIncomeTaxExpenseBenefit	-158800000	USD
CY2020Q3	ato	Tax Cutsand Jobs Actof2017 Changein Tax Rate Regulatory Liability TaxCutsandJobsActof2017ChangeinTaxRateRegulatoryLiability	706700000	USD
CY2019Q3	ato	Tax Cutsand Jobs Actof2017 Changein Tax Rate Regulatory Liability TaxCutsandJobsActof2017ChangeinTaxRateRegulatoryLiability	726300000	USD
CY2018Q3	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2020Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	5687000	USD
CY2019Q3	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	1586000	USD
CY2020Q3	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	74991000	USD
CY2019Q3	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	225000	USD
CY2020Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	2015000	USD
CY2019Q3	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	4552000	USD
CY2020Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	0	USD
CY2019Q3	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	1249000	USD
CY2020Q3	us-gaap	Derivative Assets Liabilities At Fair Value Net DerivativeAssetsLiabilitiesAtFairValueNet	78663000	USD
CY2019Q3	us-gaap	Derivative Assets Liabilities At Fair Value Net DerivativeAssetsLiabilitiesAtFairValueNet	-3990000	USD
CY2020Q3	ato	Derivative Asset Netof Contract Netting DerivativeAssetNetofContractNetting	80678000	USD
CY2020Q3	ato	Derivative Liability Netof Contract Netting DerivativeLiabilityNetofContractNetting	2015000	USD
CY2019Q3	ato	Derivative Asset Netof Contract Netting DerivativeAssetNetofContractNetting	1811000	USD
CY2019Q3	ato	Derivative Liability Netof Contract Netting DerivativeLiabilityNetofContractNetting	5801000	USD
CY2020Q3	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	5500000	USD
CY2019	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	3900000	USD
CY2018	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	2400000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax	53241000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax	-25966000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax	-3647000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci On Derivatives Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax	-3022000	USD
CY2020	us-gaap	Other Comprehensive Income Derivatives Qualifying As Hedges Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent	56888000	USD
CY2019	us-gaap	Other Comprehensive Income Derivatives Qualifying As Hedges Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent	-22944000	USD
CY2020Q3	ato	Accumulated Other Comprehensive Income Loss Derivatives Qualifyingas Hedges Interest Rate Agreements Realized Gain Loss Netof Tax AccumulatedOtherComprehensiveIncomeLossDerivativesQualifyingasHedgesInterestRateAgreementsRealizedGainLossNetofTax	-114500000	USD
CY2020Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2020Q3	us-gaap	Derivative Assets DerivativeAssets	80678000	USD
CY2020Q3	ato	Debtandequitysecurities Debtandequitysecurities	103952000	USD
CY2020Q3	us-gaap	Derivative Asset Fair Value Gross Liability And Obligation To Return Cash Offset DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset	0	USD
CY2020Q3	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	184630000	USD
CY2020Q3	us-gaap	Derivative Liability Fair Value Gross Asset And Right To Reclaim Cash Offset DerivativeLiabilityFairValueGrossAssetAndRightToReclaimCashOffset	0	USD
CY2020Q3	us-gaap	Derivative Liabilities DerivativeLiabilities	2015000	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
CY2020Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	32600000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	31700000	USD
CY2020Q3	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	4560000000	USD
CY2020Q3	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	5597183000	USD
CY2019Q4	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	875563000	USD
CY2020Q1	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	977665000	USD
CY2020Q2	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	492995000	USD
CY2020Q3	us-gaap	Regulated And Unregulated Operating Revenue RegulatedAndUnregulatedOperatingRevenue	474914000	USD
CY2019Q4	us-gaap	Operating Income Loss OperatingIncomeLoss	252781000	USD
CY2020Q1	us-gaap	Operating Income Loss OperatingIncomeLoss	331438000	USD
CY2020Q2	us-gaap	Operating Income Loss OperatingIncomeLoss	139035000	USD
CY2020Q3	us-gaap	Operating Income Loss OperatingIncomeLoss	100845000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	178673000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	239646000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	117791000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	65333000	USD
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.47
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.95
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.96
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.53
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.47
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.95
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.96
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.53
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
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	214888000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	80466000	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	Earnings Per Share Basic EarningsPerShareBasic	0.49
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.38
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

Files In Submission

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0000731802-20-000040-index.html	Edgar Link	pending
0000731802-20-000040.txt	Edgar Link	pending
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2020 Q3 Form 10-K Financial Statement

#000073180220000040 Filed on November 13, 2020

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$ATO Atmos Energy Corp Stock $ato

2020 Q3 Form 10-K Financial Statement

#000073180220000040 Filed on November 13, 2020

Income Statement

Balance Sheet

Cashflow Statement

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Files In Submission

$ATO
Atmos Energy Corp Stock $ato