GOVERNMENT GRANTS (Details) $ in Thousands		1 Months Ended	3 Months Ended								12 Months Ended
	Nov. 16, 2020 USD ($)	Aug. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) MW item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Government Grants
Revenue			$ 123,702	$ 111,739	$ 109,098	$ 110,905	$ 112,085	$ 115,616	$ 107,721	$ 103,300	$ 455,444	$ 438,722	$ 451,207
Payment for PALs											$ 20,396
Universal Service Fund programs
Government Grants
Number of fund disbursement programs | item											4
Universal Service Fund programs | HURRICANES IRMA AND MARIA
Government Grants
Revenue													15,500
High-Cost Support Program | US Telecom
Government Grants
Revenue											$ 1,200	1,200	1,200
High-Cost Support Program | International Telecom
Government Grants
Revenue											16,400	16,400	16,500
Grant Funds Awarded	$ 8,600												$ 16,400
Grant fund term	10 years												10 years
High-Cost Support Program | International Telecom | Grant Reduction During First Year
Government Grants
Ratio of reduction in grant amount	0.67
Amount of reduction in grant amount awarded	$ 10,900
High-Cost Support Program | International Telecom | Grant Reduction During Second Year
Government Grants
Ratio of reduction in grant amount	0.33
Amount of reduction in grant amount awarded	$ 5,500
High-Cost Support Program | International Telecom | HURRICANES IRMA AND MARIA
Government Grants
Revenue													$ 15,500
High-Cost Support Program | International Telecom | Maximum
Government Grants
Proposed grant award													18,700
E-Rate, Lifeline and Rural Health Care Support Programs
Government Grants
Revenue											10,000	6,100	8,200
Network Connectivity for Eligible Communities
Government Grants
Grant Funds Awarded											1,000	15,800
Proceeds from completion of construction												5,400
Reimbursement of capital expenditures												3,100
Offsetting operating activities											2,900	2,300
Construction obligation completed											10,200
Construction obligation yet to be completed											$ 6,600
CARES Act
Government Grants
Grant Funds Awarded			16,300
Tribal Bidding Credit
Government Grants
Wireless service spectrum (in Mhz) | MW											600
Revenue													$ 7,400
Grant funds used to offset fixed asset related costs			5,800								$ 5,800
Grant funds used to offset operating expenses			1,600								1,600
Offsetting operating activities											200
Amount spent on capital expenditure											5,800
Connect America Fund Phase II Auction
Government Grants
Revenue											7,600	$ 5,300
Grant Funds Awarded		$ 79,900
Grant fund term		10 years
CBRS Auction
Government Grants
Initial term of licenses				10 years
Payment for PALs				$ 20,400
RDOF
Government Grants
Grant funds expected to be awarded			$ 20,100								$ 20,100
Grant fund term											10 years
Number of households to receive broadband coverage | item											10,000