ACQUISITIONS - Purchase Price Allocation (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 01, 2016	May 03, 2016	Apr. 07, 2016	Jul. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Consideration Transferred
Total consideration		$ 41,563
Total value to allocate
Total consideration		41,563
Business Combination Total Value Allocation		74,472
Preliminary purchase price allocation:
Goodwill					$ 62,042		$ 62,042				$ 45,077
Gain on KeyTech bargain purchase							$ 7,304
Purchase price allocation BDC:
Discount rate (as a percent)							14.00%
Revenue					138,795	$ 96,782	$ 328,471	$ 272,453
Income (Loss) from Continuing Operations before Income Taxes					21,296	21,782	37,784	48,439
CellOne [Member]
Purchase price allocation BDC:
Acquired carrying value of BDC non-controlling interest acquired		2,940
Excess of purchase price paid over carrying value of non-controlling interest acquired		4,105
Bermuda wireless operations
Consideration Transferred
Total consideration		7,045
Total value to allocate
Total consideration		7,045
Business Combination Total Value Allocation		7,045
Vibrant Energy
Consideration Transferred
Total consideration			$ 6,193
Total value to allocate
Total consideration			6,193
Preliminary purchase price allocation:
Cash			136
Property, plant and equipment			7,321
Goodwill			3,279
Accounts payable and accrued liabilities			(5,179)
Net assets acquired			6,193
Prepayments and other assets			$ 636
Purchase price allocation BDC:
Revenue							300
Keytech
Consideration Transferred
Total consideration		34,518
Non-controlling interests		32,909
Total value to allocate
Total consideration		34,518
Business Combination Total Value Allocation		67,427
Preliminary purchase price allocation:
Cash		8,185
Accounts receivable		6,451
Other current assets		3,241
Property, plant and equipment		100,892
Intangible assets		10,590
Other Assets		3,464
Accounts payable and accrued liabilities		(16,051)
Advance payments and deposits		(6,683)
Net assets acquired		74,731
Gain on KeyTech bargain purchase		7,304
Current debt		(6,429)
Long-term debt		(28,929)
Non-controlling interests		32,909
Purchase price allocation BDC:
Revenue							34,700
Income (Loss) from Continuing Operations before Income Taxes							1,900
External acquisition related charges relating to legal, accounting and consulting services.		$ 4,300			3,300		3,300
Innovative
Consideration Transferred
Total consideration	$ 112,301
Cash-on-hand used to fund the purchase price	50,900
Working capital adjustments							4,900
Purchase price	145,000						1,400
Purchase price adjustments	4,900
Total value to allocate
Total consideration	112,301
Non-controlling interests	221
Business Combination Total Value Allocation	112,522
Preliminary purchase price allocation:
Cash	4,229
Accounts receivable	6,553
Materials & supplies	6,533
Other current assets	2,286
Property, plant and equipment	108,284
Telecommunication licenses	7,623
Goodwill	20,586
Intangible assets	7,800
Other Assets	4,394
Accounts payable and accrued liabilities	(15,889)
Advance payments and deposits	(7,793)
Deferred tax liability	(2,935)
Pension liability	(29,149)
Net assets acquired	112,522
Purchase price allocation BDC:
Revenue							26,500
Income (Loss) from Continuing Operations before Income Taxes							1,400
External acquisition related charges relating to legal, accounting and consulting services.	4,300				$ 2,400		2,400
Innovative | Defined Benefit Pension Plans
Funded status of plan
Fair value of plan assets										$ 45,117
Benefit obligations										69,178
Funded status of plan										(24,061)
Innovative | Other Post-retirement Benefit Plans
Funded status of plan
Benefit obligations										5,472
Funded status of plan										$ (5,472)
Innovative | Term loans
Consideration Transferred
Debt instrument, face amount	$ 60,000
Telecommunication Equipment
Purchase price allocation BDC:
Discounted rate used for cash flows		15.00%
US Telecom
Consideration Transferred
Total consideration				$ 9,100
Total value to allocate
Total consideration				9,100
Preliminary purchase price allocation:
Property, plant and equipment				10,200
Goodwill				600
Other long term liabilities				$ 1,700
As reported
Pro Forma (unaudited)
Revenue						96,782	328,471	272,453
Net income attributable to ATN stockholders						$ 6,576	$ 10,206	$ 12,757
Earnings per shares:
Earnings per share: Basic (in dollars per share)						$ 0.41	$ 0.63	$ 0.79
Earnings per share: Diluted (in dollars per share)						$ 0.41	$ 0.63	$ 0.79
Forecast | Innovative
Consideration Transferred
Cash-on-hand used to fund the purchase price									$ 27,800
Minimum | Defined Benefit Pension Plans
Funded status of plan
Discounted rate used for pension benefit obligation							3.60%
Minimum | Innovative | Income Approach | Non-Controlling Interests
Purchase price allocation BDC:
Discount rate (as a percent)							15.00%
Minimum | Innovative | Income Approach | Cash flow
Purchase price allocation BDC:
Discount rate (as a percent)							14.00%
Minimum | Telecommunication Equipment
Purchase price allocation BDC:
Useful life	1 year	3 years
Minimum | Telecommunication Equipment | Customer relationships
Purchase price allocation BDC:
Useful life	9 years
Maximum | Defined Benefit Pension Plans
Funded status of plan
Discounted rate used for pension benefit obligation							3.90%
Maximum | Innovative | Income Approach | Non-Controlling Interests
Purchase price allocation BDC:
Discount rate (as a percent)							25.00%
Maximum | Innovative | Income Approach | Cash flow
Purchase price allocation BDC:
Discount rate (as a percent)							25.00%
Maximum | Telecommunication Equipment
Purchase price allocation BDC:
Useful life	18 years	18 years
Maximum | Telecommunication Equipment | Customer relationships
Purchase price allocation BDC:
Useful life	16 years