XML 41 R32.htm IDEA: XBRL DOCUMENT
v3.22.2

Unaudited Financial Information - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands | Jun. 30, 2022 | Sep. 30, 2021
--- | --- | ---
Regulatory Asset [Line Items] |  |
Regulatory assets | $ 2,513,357 | $ 2,521,441
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 1,310,804 | 1,424,195
Regulatory excess deferred taxes |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 586,149 | 705,084
Regulatory cost of removal obligation |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 558,542 | 541,511
Deferred gas costs |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 45,874 | 52,553
Asset retirement obligation |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 18,373 | 18,373
APT annual adjustment mechanism |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 26,689 | 31,110
Pension and postretirement benefit costs |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 51,954 | 56,201
Other |  |
Regulatory Liabilities [Line Items] |  |
Regulatory liabilities | 23,223 | 19,363
Pension and postretirement benefit costs |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 34,482 | 45,922
Infrastructure mechanisms |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 225,279 | 222,795
Winter Storm Uri incremental costs |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 2,107,820 | 2,100,728
Deferred gas costs |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 42,818 | 66,395
Regulatory excess deferred taxes |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 48,746 | 45,370
Recoverable loss on reacquired debt |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 3,448 | 3,789
Deferred pipeline record collection costs |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | 35,212 | 32,099
Other |  |
Regulatory Asset [Line Items] |  |
Regulatory assets | $ 15,552 | $ 4,343

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_RegulatoryAssetLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
Name: | us-gaap_RegulatoryLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_RegulatoryLiabilitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_DeferredIncomeTaxChargesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_RemovalCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_DeferredFuelCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_AssetRetirementObligationCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=ato_RegulatoryClauseRevenuesOverRecoveredMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_PensionAndOtherPostretirementPlansCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=us-gaap_OtherRegulatoryAssetsLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_PensionAndOtherPostretirementPlansCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=ato_InfrastructureMechanismsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_StormCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_DeferredFuelCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_DeferredIncomeTaxChargesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_LossOnReacquiredDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_DeferredProjectCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_OtherRegulatoryAssetsLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |