CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Noncontrolling interest income tax expense (benefit)	$ (1.2)	$ 0.2	$ (0.8)	$ 0.8

Amount of current income tax expense (benefit) reported by noncontrolling interests.

No definition available.

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