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ACQUISITIONS AND DISPOSITIONS - Pro Forma Results (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	9 Months Ended
	Jul. 01, 2016	May 03, 2016	Sep. 30, 2016	Sep. 30, 2016
One Communications (formerly KeyTech)
Acquisition
Retirement of debt		$ 24,700
Viya (formerly Innovative)
Acquisition
Retirement of debt	$ 185,800
Viya (formerly Innovative) \| Term loans
Acquisition
Debt Instrument, Face Amount	$ 60,000
One Communications and Viya
Pro Forma
Revenue			$ 407,096
Net income (loss) attributable to ATN International, Inc. Stockholders			$ 12,768
Earnings per share: Basic (in dollars per share)			$ 0.79
Earnings per share: Diluted (in dollars per share)			$ 0.79
One Communications and Viya \| As reported
Pro Forma
Revenue			$ 328,471
Net income (loss) attributable to ATN International, Inc. Stockholders			$ 10,206
Earnings per share: Basic (in dollars per share)			$ 0.63
Earnings per share: Diluted (in dollars per share)			$ 0.63
One Communications and Viya
Acquisition
Impairment charges				$ 5,400