GOVERNMENT GRANTS (Details) - Mobility Funds - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2017	Sep. 30, 2017
MOBILITY FUND GRANTS
Mobility Funds received		$ 21.1
Period over which a portion of the Mobility Funds is used to offset the costs of supporting the networks	5 years
U.S. Telecom
MOBILITY FUND GRANTS
Mobility Funds received		21.1
Grant funds used to offset operating expenses		13.9
Mobility funds received and recorded to date		9.0
U.S. Telecom \| Property, Plant and Equipment
MOBILITY FUND GRANTS
Grant funds used to offset fixed asset related costs		7.2
U.S. Telecom \| Other current liabilities
MOBILITY FUND GRANTS
Grant funds used to offset operating expenses		$ 4.9

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.

No definition available.

+ Details

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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

Amount of Mobility Funds received by the entity since inception of the grant and recorded to date.

+ References

No definition available.

+ Details

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

- Definition

Represents the period over which a portion of the Mobility Funds is used to offset the costs of supporting the networks.

+ References

No definition available.

+ Details

Name:	atni_PeriodOverWhichMobilityFundUsedToOffsetCostsOfSupportingTheNetworks
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	atni_TypeOfMobilityFundAxis=atni_WholesaleMobilityFundsMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_PropertyPlantAndEquipmentMember
Namespace Prefix:
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- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentLiabilitiesMember
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Data Type:	na
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