REVENUE RECOGNITION AND RECEIVABLES - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Contract Assets and Liabilities
Contract Asset - current		$ 2,413
Change in contract asset - current		(196)
Contract Asset - current	$ 2,217	$ 2,217
% of change in contract asset - current		(8.00%)
Contract asset, noncurrent		$ 905
Change in contract Asset - noncurrent		(254)
Contract asset, noncurrent	651	$ 651
% of change in contract Asset - noncurrent		(28.00%)
Contract liability- current		$ (15,044)
Change in contract liabilities - current		1,446
Contract liability- current	(13,598)	$ (13,598)
% of change in contract liabilities - current		10.00%
Contract liability- noncurrent		$ (5,450)
Change in contract liabilities - noncurrent		257
Contract liability- noncurrent	(5,193)	$ (5,193)
% of change in contract liabilities - Noncurrent		5.00%
Net contract liability		$ (17,176)
Change in net contract liability		1,253
Net contract liability	(15,923)	$ (15,923)
% of change in net contract liability		7.00%
Revenue recognized related to contract liability		$ 13,200
Amortization of contract assets	$ 600	1,300
Revenue recognized in the period related to performance obligations that were satisfied or partially satisfied in previous periods		$ 0
Retail revenue period for billing postpaid customers in advance		1 month