REVENUE RECOGNITION - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Contract Assets and Liabilities
Contract asset, current	$ 2,010	$ 1,900
Change in contract asset - current	$ 110
% of change in contract asset - current	6.00%
Contract asset, noncurrent	$ 779	802
Change in contract Asset – noncurrent	$ (23)
% of change in contract Asset – noncurrent	(3.00%)
Contract liabilities	$ (15,239)	(13,787)
Change in contract liabilities	$ (1,452)
% of change in contract liabilities	11.00%
Net contract liability	$ (12,450)	$ (11,085)
Change in net contract liability	$ (1,365)
% of change in net contract liability	12.00%
Revenue recognized related to contract liability	$ 9,100
Amortization of contract assets	$ 600

Represents the amortization of contract assets into revenue.

No definition available.

Name:	atni_AmortizationOfContractAssetsIntoRevenue
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) in revenue recognized for current cumulative catch-up adjustment from the timing of customer prepayments and contract billings which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

No definition available.

+ Details

Name:	atni_ContractWithCustomerAssetCurrentCumulativeCatchUpAdjustmentToRevenueTimingOfCustomerPrepaymentsAndContractBillings
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time net of amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

No definition available.

+ Details

Name:	atni_ContractWithCustomerAssetLiabilityNet
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from the timing of customer prepayments and contract billings which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

No definition available.

+ Details

Name:	atni_ContractWithCustomerAssetLiabilityNetCumulativeCatchUpAdjustmentToRevenueTimingOfCustomerPrepaymentsAndContractBillings
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) in revenue recognized for noncurrent cumulative catch-up adjustment from the timing of customer prepayments and contract billings which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

No definition available.

+ Details

Name:	atni_ContractWithCustomerAssetNoncurrentCumulativeCatchUpAdjustmentToRevenueTimingOfCustomerPrepaymentsAndContractBillings
Namespace Prefix:	atni_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the percentage of change in current contract with customers assets.

+ References

No definition available.

+ Details

Name:	atni_PercentageOfChangeInContractWithCustomerAssetsCurrent
Namespace Prefix:	atni_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of change in noncurrent contract with customers assets.

+ References

No definition available.

+ Details

Name:	atni_PercentageOfChangeInContractWithCustomerAssetsNoncurrent
Namespace Prefix:	atni_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of change in contract with customers liabilities.

+ References

No definition available.

+ Details

Name:	atni_PercentageOfChangeInContractWithCustomerLiability
Namespace Prefix:	atni_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of change in contract with customers net assets liabilities.

+ References

No definition available.

+ Details

Name:	atni_PercentageOfChangeInContractWithCustomerNetAssetsLiability
Namespace Prefix:	atni_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_ChangeInContractWithCustomerAssetAndLiabilityAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_ContractWithCustomerAssetNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

+ References

+ Details

Name:	us-gaap_ContractWithCustomerAssetNetNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

+ Details

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which (increases) decreases obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130551-203045

+ Details

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

- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

+ Details

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