GOODWILL AND INTANGIBLE ASSETS - Change In Carrying Amount Of Telecommunications Licenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in the carrying amount of the company's telecommunications licenses, by operating segment
Balance at the beginning of the period	$ 93,686
Balance at the end of the period	114,083	$ 93,686
Telecommunications Licenses
Telecommunications licenses
Impairment of intangible assets		0	$ 0
Changes in the carrying amount of the company's telecommunications licenses, by operating segment
Balance at the beginning of the period	93,686	93,686
Acquired licenses	20,397	0
Dispositions	0	0
Transfers	0
Balance at the end of the period	114,083	93,686	93,686
Telecommunications Licenses | International Telecom
Changes in the carrying amount of the company's telecommunications licenses, by operating segment
Balance at the beginning of the period	23,347	23,347
Acquired licenses	200	0
Dispositions	0	0
Transfers	11,251
Balance at the end of the period	34,798	23,347	23,347
Telecommunications Licenses | US Telecom
Changes in the carrying amount of the company's telecommunications licenses, by operating segment
Balance at the beginning of the period	70,339	70,339
Acquired licenses	20,197	0
Dispositions	0	0
Transfers	(11,251)
Balance at the end of the period	$ 79,285	$ 70,339	$ 70,339