CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF OPERATIONS
Noncontrolling interest income tax expense	$ 1.1	$ 1.3	$ 1.5

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