Revenue Recognition - Impacts of adoption in the current period - IS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue									$ 451,207
Sales, marketing and customer service									35,207	$ 35,184	$ 30,253
Total operating expenses	$ 97,488	$ 90,395	$ 102,035	$ 100,266	$ 66,387	$ 141,697	$ 107,442	$ 110,359	390,184	425,885	405,733
Income from operations	10,318	30,743	15,753	4,209	41,314	(19,565)	15,803	17,756	61,023	55,308	51,270
Income before taxes	11,336	27,920	12,868	1,618	41,196	(21,860)	13,505	14,712	53,742	47,553	45,374
Income tax provisions (benefit)	5,851	7,010	2,088	3,921	(6,181)	(884)	2,596	3,128	18,870	(1,341)	21,160
Net income	5,485	20,910	10,780	(2,303)	47,377	(20,976)	10,909	11,584	34,872	48,894	24,214
Net income attributable to non-controlling interests, net of tax	(4,354)	(3,887)	(3,564)	(3,252)	(3,871)	(3,784)	(5,026)	(4,725)	(15,057)	(17,406)	(12,113)
Net income attributable to ATN International, Inc. stockholders	$ 1,131	$ 17,023	$ 7,216	$ (5,555)	$ 43,506	$ (24,760)	$ 5,883	$ 6,859	19,815	$ 31,488	$ 12,101
ASU 2014-09 | Change
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue									1,075
Sales, marketing and customer service									(755)
Total operating expenses									(755)
Income from operations									1,830
Income before taxes									1,830
Income tax provisions (benefit)									131
Net income									1,699
Net income attributable to non-controlling interests, net of tax									(706)
Net income attributable to ATN International, Inc. stockholders									993
ASU 2014-09 | Under previous guidance
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue									450,132
Sales, marketing and customer service									35,962
Total operating expenses									390,939
Income from operations									59,193
Income before taxes									51,912
Income tax provisions (benefit)									18,739
Net income									33,173
Net income attributable to non-controlling interests, net of tax									(14,351)
Net income attributable to ATN International, Inc. stockholders									18,822
Wireless
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue									198,824
Wireless | ASU 2014-09 | Change
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue									1,075
Wireless | ASU 2014-09 | Under previous guidance
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue									$ 197,749