EQUITY (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stockholders' equity
Equity, beginning of period	$ 830,223	$ 809,169
Stock-based compensation	1,576	1,666
Comprehensive income:
Net income (loss)	(2,303)	11,584
Projected pension benefit obligation, net of tax of $0 and $0.4 million		513
Unrealized gain (loss) on securities	139	(41)
Reclassifications of gains on sale of marketable securities to net income		(289)
Foreign currency translation adjustment	(1,032)	1,930
Comprehensive income (loss)	(3,196)	13,697
Issuance of common stock upon exercise of stock options	498	95
Dividends declared on common stock	(15,181)	(5,460)
Distributions to non-controlling interests		(2,888)
Investments made by non-controlling interests		69
Loss on deconsolidation of subsidiary		529
Repurchase of non-controlling interests	(2)	(819)
Purchase of treasury stock	(2,538)	(2,215)
Equity, end of period	814,015	813,953
ASU 2016-09
Comprehensive income:
Change in accounting method- adoption		110
ASU 2014-09
Comprehensive income:
Change in accounting method- adoption	2,635
Total ATNI Stockholders' Equity
Stockholders' equity
Equity, beginning of period	688,727	677,055
Stock-based compensation	1,576	1,666
Comprehensive income:
Net income (loss)	(5,555)	6,859
Projected pension benefit obligation, net of tax of $0 and $0.4 million		513
Unrealized gain (loss) on securities	139	(41)
Reclassifications of gains on sale of marketable securities to net income		(289)
Foreign currency translation adjustment	(1,032)	1,930
Comprehensive income (loss)	(6,448)	8,972
Issuance of common stock upon exercise of stock options	498	95
Dividends declared on common stock	(2,696)	(5,460)
Repurchase of non-controlling interests		(670)
Purchase of treasury stock	(2,538)	(2,215)
Equity, end of period	680,607	679,553
Total ATNI Stockholders' Equity | ASU 2016-09
Comprehensive income:
Change in accounting method- adoption		110
Total ATNI Stockholders' Equity | ASU 2014-09
Comprehensive income:
Change in accounting method- adoption	1,488
Non-Controlling Interests
Stockholders' equity
Equity, beginning of period	141,496	132,114
Comprehensive income:
Net income (loss)	3,252	4,725
Comprehensive income (loss)	3,252	4,725
Dividends declared on common stock	(12,485)
Distributions to non-controlling interests		(2,888)
Investments made by non-controlling interests		69
Loss on deconsolidation of subsidiary		529
Repurchase of non-controlling interests	(2)	(149)
Equity, end of period	133,408	$ 136,134
Non-Controlling Interests | ASU 2014-09
Comprehensive income:
Change in accounting method- adoption	$ 1,147