GOVERNMENT GRANTS (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Aug. 31, 2018 USD ($)	Mar. 31, 2020 USD ($) MW item	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Government Grants
Revenue		$ 110,905	$ 103,300
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
Mobility Funds
Government Grants
Mobility Funds received							$ 21,100
Mobility Funds | US Telecom
Government Grants
Grant funds used to offset fixed asset related costs							$ 7,200
Grant funds used to offset operating expenses						$ 13,900
High-Cost Support Program | US Telecom
Government Grants
Revenue		$ 300	300
High-Cost Support Program | International Telecom
Government Grants
Revenue		4,100	4,100
E-Rate, Lifeline and Rural Health Care Support Programs
Government Grants
Revenue		2,200	$ 1,500
E-Rate
Government Grants
Grant Funds Awarded		$ 15,800
Proceeds from completion of construction				$ 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
Grant funds used to offset operating expenses		2,000
Connect America Fund Phase II Auction
Government Grants
Revenue		$ 1,900
Grant Funds Awarded	$ 79,900
Grant fund term	10 years