SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($) item
Segment reporting
Number of reportable segments | item									5	4	4
Revenue
Revenue	$ 82,916	$ 96,782	$ 90,326	$ 85,345	$ 88,511	$ 89,393	$ 83,269	$ 75,174	$ 355,369	$ 336,347	$ 292,835
Depreciation and amortization									56,890	51,234	48,737
Non-cash stock-based compensation									4,975	4,323	4,454
Operating income (loss)	8,181	$ 22,524	$ 28,732	$ 19,158	19,563	$ 28,158	$ 21,607	$ 16,248	78,595	85,576	64,085
Segment Assets
Net fixed assets	373,503				369,582				373,503	369,582
Goodwill	45,077				45,077				45,077	45,077
Total assets	945,004				925,030				945,004	925,030
Capital Expenditures
Capital expenditures									64,753	58,300	69,316
U.S. Wireless
Revenue
Revenue									155,390	153,040	107,930
International wireless
Revenue
Revenue									81,652	88,650	91,432
Wireline
Revenue
Revenue									86,485	85,284	84,585
Equipment and other
Revenue
Revenue									10,802	9,373	8,888
Renewable energy
Revenue
Revenue									21,040
Reconciling Items
Revenue
Depreciation and amortization									4,947	3,980	2,967
Non-cash stock-based compensation									4,708	4,323	4,454
Operating income (loss)									(30,784)	(26,399)	(25,978)
Segment Assets
Net fixed assets	14,085				14,655				14,085	14,655
Total assets	315,740				287,349				315,740	287,349
Capital Expenditures
Capital expenditures									4,323	3,464
Reconciling Items | Discontinued operations
Segment Assets
Total assets					175					175
U.S. Wireless
Revenue
Revenue										154,592	109,005
Depreciation and amortization										14,345	14,308
Operating income (loss)										89,187	54,867
Segment Assets
Net fixed assets	89,466				79,910				89,466	79,910
Goodwill	32,148				32,148				32,148	32,148
Total assets	182,669				188,377				182,669	188,377
U.S. Wireless | U.S. Wireless
Revenue
Revenue										153,040	107,930
U.S. Wireless | Wireline
Revenue
Revenue										609	610
U.S. Wireless | Equipment and other
Revenue
Revenue										943	465
U.S. Wireless | Operating segments
Revenue
Revenue									158,128
Depreciation and amortization									17,605
Operating income (loss)									78,357
Capital Expenditures
Capital expenditures									29,741	33,446
U.S. Wireless | Operating segments | U.S. Wireless
Revenue
Revenue									155,390
U.S. Wireless | Operating segments | Wireline
Revenue
Revenue									613
U.S. Wireless | Operating segments | Equipment and other
Revenue
Revenue									2,125
International Integrated Telephony
Revenue
Revenue										86,932	93,446
Depreciation and amortization										17,408	17,975
Operating income (loss)										19,628	27,662
Segment Assets
Net fixed assets	110,063				108,972				110,063	108,972
Total assets	207,023				202,171				207,023	202,171
International Integrated Telephony | International wireless
Revenue
Revenue										26,819	30,334
International Integrated Telephony | Wireline
Revenue
Revenue										59,129	61,475
International Integrated Telephony | Equipment and other
Revenue
Revenue										984	1,637
International Integrated Telephony | Operating segments
Revenue
Revenue									88,893
Depreciation and amortization									16,470
Operating income (loss)									15,738
Capital Expenditures
Capital expenditures									14,549	10,646
International Integrated Telephony | Operating segments | International wireless
Revenue
Revenue									25,706
International Integrated Telephony | Operating segments | Wireline
Revenue
Revenue									61,244
International Integrated Telephony | Operating segments | Equipment and other
Revenue
Revenue									1,943
Island Wireless
Revenue
Revenue										68,575	67,653
Depreciation and amortization										10,671	10,305
Operating income (loss)										9,046	8,610
Segment Assets
Net fixed assets	23,199				26,590				23,199	26,590
Goodwill	5,438				5,438				5,438	5,438
Total assets	71,747				74,563				71,747	74,563
Island Wireless | International wireless
Revenue
Revenue										61,831	61,098
Island Wireless | Equipment and other
Revenue
Revenue										6,744	6,555
Island Wireless | Operating segments
Revenue
Revenue									62,450
Depreciation and amortization									8,413
Operating income (loss)									12,462
Capital Expenditures
Capital expenditures									8,255	6,064
Island Wireless | Operating segments | International wireless
Revenue
Revenue									55,946
Island Wireless | Operating segments | Equipment and other
Revenue
Revenue									6,504
U.S. Wireline
Revenue
Revenue										25,799	22,731
Depreciation and amortization										4,725	3,182
Operating income (loss)										(3,668)	(1,076)
Segment Assets
Net fixed assets	30,130				28,113				30,130	28,113
Goodwill	7,491				7,491				7,491	7,491
Total assets	45,038				42,446				45,038	42,446
U.S. Wireline | Wireline
Revenue
Revenue										25,546	22,500
U.S. Wireline | Equipment and other
Revenue
Revenue										253	$ 231
U.S. Wireline | Operating segments
Revenue
Revenue									24,858
Depreciation and amortization									4,635
Operating income (loss)									(3,898)
Capital Expenditures
Capital expenditures									7,847	4,680
U.S. Wireline | Operating segments | Wireline
Revenue
Revenue									24,628
U.S. Wireline | Operating segments | Equipment and other
Revenue
Revenue									230
Renewable energy
Revenue
Revenue										449
Depreciation and amortization										105
Operating income (loss)										(2,218)
Segment Assets
Net fixed assets	106,560				111,342				106,560	111,342
Total assets	$ 122,788				$ 130,124				122,788	130,124
Renewable energy | Equipment and other
Revenue
Revenue										$ 449
Renewable energy | Operating segments
Revenue
Revenue									21,040
Depreciation and amortization									4,820
Non-cash stock-based compensation									267
Operating income (loss)									6,720
Capital Expenditures
Capital expenditures									38
Renewable energy | Operating segments | Renewable energy
Revenue
Revenue									$ 21,040