SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment reporting
Number of reportable segments | segment				3
Revenue
Revenue	$ 115,616	$ 121,138		$ 326,637	$ 343,401
Depreciation and amortization	22,603	21,384		64,870	64,602
Non-cash stock-based compensation	1,548	1,393		4,881	5,071
Operating income (loss)	10,248	30,824		15,117	50,786
Segment Assets
Cash, Cash equivalents, and Investments	168,530			168,530		$ 192,229
Total current assets	257,811			257,811		275,765
Fixed assets, net	605,501			605,501		626,852
Goodwill	63,970			63,970		63,970
Total assets	1,162,800			1,162,800		1,107,304
Total current liabilities	141,030			141,030		140,650
Total debt	88,265			88,265		90,982
Capital Expenditures
Capital expenditures				49,486	154,278
Hurricane rebuild capital expenditures				123	78,903
Hurricane insurance proceeds					34,606
Wireless
Revenue
Revenue	54,555	52,003		143,705	153,046
Wireline
Revenue
Revenue	59,623	63,717		178,555	173,083
Renewable Energy
Revenue
Revenue	1,438	5,418		4,377	17,272
Corporate and Other
Revenue
Depreciation and amortization	1,728	1,459		4,973	4,190
Non-cash stock-based compensation	1,263	1,344		4,575	4,917
Operating income (loss)	(7,817)	(8,011)		(25,862)	(26,189)
Segment Assets
Cash, Cash equivalents, and Investments	59,584			59,584		78,043
Total current assets	57,220			57,220		83,107
Fixed assets, net	22,024			22,024		20,381
Total assets	185,624			185,624		181,789
Total current liabilities	33,458			33,458		38,827
Capital Expenditures
Capital expenditures				5,611	6,385
US Telecom | Operating segments
Revenue
Revenue	32,893	31,808		80,799	90,591
Depreciation and amortization	5,770	5,665		16,919	19,013
Operating income (loss)	7,912	22,773		5,927	35,839
Segment Assets
Cash, Cash equivalents, and Investments	36,738			36,738		19,118
Total current assets	60,782			60,782		36,801
Fixed assets, net	69,642			69,642		78,102
Goodwill	35,269			35,269		35,269
Total assets	230,585			230,585		172,634
Total current liabilities	30,870			30,870		15,783
Capital Expenditures
Capital expenditures				8,533	9,461
US Telecom | Operating segments | Wireless
Revenue
Revenue	32,168	29,784		78,261	85,767
US Telecom | Operating segments | Wireline
Revenue
Revenue	725	2,024		2,538	4,824
International Telecom | Operating segments
Revenue
Revenue	81,285	83,912		241,461	235,538
Depreciation and amortization	14,089	12,441		40,709	35,907
Non-cash stock-based compensation	285	20		306	68
Operating income (loss)	10,867	16,239		35,802	37,449
Segment Assets
Cash, Cash equivalents, and Investments	51,178			51,178		32,390
Total current assets	101,113			101,113		75,304
Fixed assets, net	470,338			470,338		482,770
Goodwill	25,421			25,421		25,421
Total assets	660,367			660,367		622,454
Total current liabilities	75,348			75,348		82,575
Total debt	88,265			88,265		90,970
Capital Expenditures
Capital expenditures				33,159	136,790
Hurricane rebuild capital expenditures				100		78,900
Hurricane insurance proceeds			$ 34,600
International Telecom | Operating segments | Wireless
Revenue
Revenue	22,387	22,219		65,444	67,279
International Telecom | Operating segments | Wireline
Revenue
Revenue	58,898	61,693		176,017	168,259
Renewable Energy | Operating segments
Revenue
Revenue	1,438	5,418		4,377	17,272
Depreciation and amortization	1,016	1,819		2,269	5,492
Non-cash stock-based compensation		29			86
Operating income (loss)	(714)	(177)		(750)	3,687
Segment Assets
Cash, Cash equivalents, and Investments	21,030			21,030		62,678
Total current assets	38,696			38,696		80,553
Fixed assets, net	43,497			43,497		45,599
Goodwill	3,280			3,280		3,280
Total assets	86,224			86,224		130,427
Total current liabilities	1,354			1,354		3,465
Total debt						$ 12
Capital Expenditures
Capital expenditures				2,183	1,642
Renewable Energy | Operating segments | Renewable Energy
Revenue
Revenue	$ 1,438	$ 5,418		$ 4,377	$ 17,272