XML 69 R48.htm IDEA: XBRL DOCUMENT
v3.25.3

Nature of Business (Details) customer in Millions | Sep. 30, 2025 regulated_distribution_division facility customer mi
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Product Information [Line Items] |
Number of customers serviced | customer | 3.4
Number of regulated distribution divisions | regulated_distribution_division | 6
Number of underground storage facilities | facility | 5
State of Louisiana | Pipeline and Storage |
Product Information [Line Items] |
Length of pipeline | mi | 21

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- Definition Length of Pipeline + References No definition available. + Details
Name: | ato_LengthOfPipeline
Namespace Prefix: | ato_
Data Type: | dtr-types:lengthItemType
Balance Type: | na
Period Type: | instant

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- Definition Number Of Customers, Regulated Distribution + References No definition available. + Details
Name: | ato_NumberOfCustomersRegulatedDistribution
Namespace Prefix: | ato_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Represents the number of regulated distribution divisions. + References No definition available. + Details
Name: | ato_NumberOfDivisionsRegulatedDistribution
Namespace Prefix: | ato_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Number of Underground Storage Facilities + References No definition available. + Details
Name: | ato_NumberOfUndergroundStorageFacilities
Namespace Prefix: | ato_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- 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_ProductInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_StatementGeographicalAxis=stpr_LA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=ato_PipelineandStorageSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |