GOVERNMENT GRANTS (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2018 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) MW item	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Government Grants
Revenue		$ 111,739	$ 115,616	$ 331,743	$ 326,637
Payment for PALs				$ 20,396
Universal Service Fund programs
Government Grants
Number of fund disbursement programs | item				4
High-Cost Support Program | US Telecom
Government Grants
Revenue		300	300	$ 900	900
High-Cost Support Program | International Telecom
Government Grants
Revenue		4,100	4,100	12,300	12,300
E-Rate, Lifeline and Rural Health Care Support Programs
Government Grants
Revenue		2,200	1,500	6,600	4,700
Network Connectivity for Eligible Communities
Government Grants
Grant Funds Awarded				16,800
Proceeds from completion of construction				$ 0		$ 5,400
Reimbursement of capital expenditures						3,100
Offsetting operating activities						$ 2,300
Tribal Bidding Credit
Government Grants
Wireless service spectrum (in Mhz) | MW				600
Revenue							$ 7,400
Grant funds used to offset fixed asset related costs		5,400		$ 5,400
Grant funds used to offset operating expenses		2,000		2,000
Offsetting operating activities				100
Amount spent on capital expenditure				5,100
Connect America Fund Phase II Auction
Government Grants
Revenue		$ 1,900	$ 1,900	$ 5,700	$ 3,400
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