DEFERRED REVENUE - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 82.0	$ 76.0
Prepaid Services, IRUs, And Deferred Non-Recurring Revenue
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 339.0	$ 333.5