QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly financial data
Total Revenue	$ 107,701	$ 122,132	$ 123,245	$ 128,115	$ 128,531	$ 138,795	$ 99,991	$ 89,686		$ 481,193	$ 457,003	$ 355,369
Operating expenses	66,344	141,657	107,402	110,322	118,620	116,714	98,079	73,793		425,725	407,206	276,774
Income from operations	41,357	(19,525)	15,843	17,793	9,911	22,081	1,912	15,893		55,468	49,797	78,595
Other income (expense), net	(161)	(2,335)	(2,338)	(3,081)	(2,321)	(785)	(853)	(464)		(7,915)	(4,423)	(22,394)
INCOME BEFORE INCOME TAXES	41,196	(21,860)	13,505	14,712	7,590	21,296	1,059	15,429		47,553	45,374	56,201
Income taxes	(6,181)	(884)	2,596	3,128	3,982	9,602	2,945	4,631		(1,341)	21,160	24,137
NET INCOME	47,377	(20,976)	10,909	11,584	3,608	11,694	(1,886)	10,798		48,894	24,214	33,156
Net income attributable to non-controlling interests, net of tax:
Continuing operations	(3,871)	(3,784)	(5,026)	(4,725)	(1,712)	(4,523)	(1,200)	(4,678)
NET INCOME ATTRIBUTABLE TO ATN INTERNATIONAL, INC. STOCKHOLDERS	$ 43,506	$ (24,760)	$ 5,883	$ 6,859	$ 1,896	$ 7,171	$ (3,086)	$ 6,120		$ 31,488	$ 12,101	$ 16,940
Net income (loss) per weighted average basic share attributable to ATN International, Inc. stockholders
Continuing operations (in dollars per share)	$ 2.71	$ (1.53)	$ 0.36	$ 0.42	$ 0.12	$ 0.44	$ (0.19)	$ 0.38		$ 1.95	$ 0.75	$ 0.99
Total (in dollars per share)	2.71	(1.53)	0.36	0.42	0.12	0.44	(0.19)	0.38		1.95	0.75	1.06
Net income (loss) per weighted average diluted share attributable to ATN International, Inc. stockholders
Continuing operations (in dollars per share)	2.71	(1.53)	0.36	0.42	0.12	0.44	(0.19)	0.38		1.94	0.75	0.99
Total (in dollars per share)	$ 2.71	$ (1.53)	$ 0.36	$ 0.42	$ 0.12	$ 0.44	$ (0.19)	$ 0.38		$ 1.94	$ 0.75	$ 1.06
Additional information:
Reclassification, decrease (increase) to expense					$ (800)
International | Operating Expense
Additional information:
Understatement of expense									$ 300
Renewable Energy | Revenue
Additional information:
Understatement of revenue									$ 500