SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Computation of basic and diluted earnings per share (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income (loss)	$ (20,809)	$ (708)	$ 1,967
Net income attributable to noncontrolling interests	(1,299)	(13,414)	(12,773)
NET LOSS ATTRIBUTABLE TO ATN INTERNATIONAL, INC. STOCKHOLDERS	(22,108)	(14,122)	(10,806)
Less: Preferred dividend	(1,962)
Net loss attributable to ATN International, Inc. stockholders- Diluted	$ (24,070)	$ (14,122)	$ (10,806)
Denominator:
Weighted-average shares outstanding- Basic	15,867	15,923	15,983
Weighted-average shares outstanding- Diluted	15,867	15,923	15,983