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v3.25.3

LONG-TERM DEBT - Covenants tested on an annual basis (Details) - OneVI Debt | Sep. 30, 2025
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Years 1-3 |
Short-Term Debt [Line Items] |
Annual principal repayment | 8.00%
Years 4-6 |
Short-Term Debt [Line Items] |
Annual principal repayment | 10.00%
Years 7-8 |
Short-Term Debt [Line Items] |
Annual principal repayment | 15.00%
Year 9 |
Short-Term Debt [Line Items] |
Annual principal repayment | 18.00%

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- Definition Percentage of annual principal repayment for debt instrument. + References No definition available. + Details
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Namespace Prefix: | atni_
Data Type: | dtr-types:percentItemType
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_ShortTermDebtLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_DebtInstrumentAxis=atni_OneviDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_StatementScenarioAxis=atni_PaymentOnFirstToThirdYearMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_StatementScenarioAxis=atni_PaymentOnFourthToSixthYearMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |