REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 325,662	$ 338,649
Receivables, contract assets and contract liabilities
Accounts receivable, net	122,340	132,326
Contract assets	19,704	13,897
Contract liabilities	52,905	55,212
Recognized expenses related to deferred contract acquisition costs.	2,100	1,200
Recognized revenue related to deferred revenue	$ 111,200	94,000
Revenue, Practical Expedient, Remaining Performance Obligation	true
Minimum
Receivables, contract assets and contract liabilities
Payment term	30 days
Maximum
Receivables, contract assets and contract liabilities
Payment term	60 days
Commercial and carrier
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 147,004	151,372
Commercial and carrier - Data and transport services (including VoIP)
Disaggregation of Revenue [Line Items]
Total operating revenues	89,572	88,126
Commercial and carrier - Voice services
Disaggregation of Revenue [Line Items]
Total operating revenues	45,720	48,070
Commercial and carrier - Other
Disaggregation of Revenue [Line Items]
Total operating revenues	11,712	15,176
Subsidies
Disaggregation of Revenue [Line Items]
Total operating revenues	18,454	18,159
Consumer
Disaggregation of Revenue [Line Items]
Total operating revenues	126,383	129,700
Consumer - Broadband (VoIP and Data)
Disaggregation of Revenue [Line Items]
Total operating revenues	64,076	63,085
Consumer - Video services
Disaggregation of Revenue [Line Items]
Total operating revenues	19,131	20,736
Consumer - Voice services
Disaggregation of Revenue [Line Items]
Total operating revenues	43,176	45,879
Network access
Disaggregation of Revenue [Line Items]
Total operating revenues	31,465	36,591
Other products and services
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 2,356	$ 2,827