Represents the term of grant funds.

No definition available.

Name:	atni_GrantFundTerm
Namespace Prefix:	atni_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of grant funds awarded.

+ References

No definition available.

+ Details

Name:	atni_GrantFundsAwarded
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of grants received for the construction of assets which are recognized as a reduction of the cost of fixed assets, a reduction of depreciation expense over the useful lives of the assets, and as a reduction of capital expenditures.

+ References

No definition available.

+ Details

Name:	atni_GrantFundsUsedToOffsetFixedAssetRelatedCosts
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the amount of grants received that offset operating costs.

+ References

No definition available.

+ Details

Name:	atni_GrantFundsUsedToOffsetOperatingExpenses
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	atni_MobilityFundLineItems
Namespace Prefix:	atni_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of Mobility Funds received by the entity since inception of the grant.

+ References

No definition available.

+ Details

Name:	atni_MobilityFundsReceived
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of fund disbursement programs to telecommunication providers.

+ References

No definition available.

+ Details

Name:	atni_NumberOfFundDisbursementPrograms
Namespace Prefix:	atni_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the wireless service spectrum band.

+ References

No definition available.

+ Details

Name:	atni_WirelessServiceSpectrumBand
Namespace Prefix:	atni_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

+ Details

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	atni_GovernmentGrantsAxis=atni_UniversalServiceFundProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	atni_GovernmentGrantsAxis=atni_PhaseIMobilityFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=atni_UsTelecommunicationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	atni_GovernmentGrantsAxis=atni_HighCostSupportProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessInterruptionLossAxis=us-gaap_NaturalDisastersAndOtherCasualtyEventsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=atni_InternationalTelecomMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	atni_GovernmentGrantsAxis=atni_ERateProgramAndLifelineAndRuralHealthCareSupportProgramsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	atni_GovernmentGrantsAxis=atni_ERateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	atni_GovernmentGrantsAxis=atni_TribalBiddingCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	atni_GovernmentGrantsAxis=atni_ConnectAmericaFundPhaseIiAuctionMember
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GOVERNMENT GRANTS (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
GOVERNMENT GRANTS (Details) $ in Millions	Aug. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) item	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Universal Service Fund programs
Government Grants
Number of fund disbursement programs \| item				4
Mobility Funds
Government Grants
Mobility Funds received		$ 21.1		$ 21.1
Mobility Funds \| US Telecom
Government Grants
Grant funds used to offset fixed asset related costs		7.2		7.2
Grant funds used to offset operating expenses		13.9		13.9
High-Cost Support Program \| HURRICANES IRMA AND MARIA
Government Grants
Revenue			$ 7.2		$ 15.4
High-Cost Support Program \| US Telecom
Government Grants
Revenue		0.3	0.3	0.9	0.9
High-Cost Support Program \| International Telecom
Government Grants
Revenue		4.1	4.1	12.3	12.4
E-Rate, Lifeline and Rural Health Care Support Programs
Government Grants
Revenue		1.5	$ 2.0	4.7	$ 6.3
E-Rate
Government Grants
Grant Funds Awarded				$ 16.6
Tribal Bidding Credit
Government Grants
Wireless service spectrum (in Mhz)				600
Revenue						$ 7.4
Grant funds used to offset fixed asset related costs		5.4		$ 5.4
Grant funds used to offset operating expenses		2.0		2.0
Connect America Fund Phase II Auction
Government Grants
Revenue		$ 1.9		$ 3.4
Grant Funds Awarded	$ 79.9
Grant fund term	10 years