XML 63 R51.htm IDEA: XBRL DOCUMENT
v3.25.3

FAIR VALUE MEASUREMENTS AND INVESTMENTS - Investments (Details) - USD ($) $ in Thousands | 9 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024
Roll forward of investments |  |
Beginning balance | $ 41,956 | $ 42,907
Income recognized | 0 | 242
Distributions |  | (602)
Sale of investments |  | (790)
Ending balance |  | 41,757
Investments without a readily determinable fair value |  |
Roll forward of investments |  |
Beginning balance | $ 41,956 | 41,710
Income recognized |  | 47
Ending balance |  | 41,757
Fair value investments |  |
Roll forward of investments |  |
Beginning balance |  | 1,197
Income recognized |  | 195
Distributions |  | (602)
Sale of investments |  | $ (790)

X
- Definition Amount of increase (decrease) from income recognized. + References No definition available. + Details
Name: | atni_InvestmentIncreaseDecreaseFromIncomeRecognized
Namespace Prefix: | atni_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of decrease from sale of investments . + References No definition available. + Details
Name: | atni_InvestmentsDecreaseFromSale
Namespace Prefix: | atni_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase (decrease) in investments from contributions (distributions). + References No definition available. + Details
Name: | atni_InvestmentsIncreaseDecreaseFromContributionsDistributions
Namespace Prefix: | atni_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | atni_InvestmentsRollForwardAbstract
Namespace Prefix: | atni_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Sum of the carrying amounts as of the balance sheet date of all investments. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-14 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 605 -Name Accounting Standards Codification -Section 55 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477548/944-605-55-11 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480078/944-80-55-14 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480078/944-80-55-9 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)(h)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)(6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 + Details
Name: | us-gaap_Investments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=atni_InvestmentWithoutReadilyDeterminableFairValueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=atni_FairValueInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |