SIGNIFICANT ACCOUNTING POLICIES - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 1,568.2	$ 1,430.3
Lease revenue									159.6	60.5
Total telecommunications services revenue	$ 423.9	$ 420.0	$ 433.8	$ 450.2	$ 454.8	$ 448.6	$ 326.7	$ 260.7	1,727.8	1,490.8	$ 827.9
United States
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									779.7	785.4
Total telecommunications services revenue									789.1	785.4	627.6
Europe
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									745.9	598.7
Total telecommunications services revenue									895.9	659.2	186.2
Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									42.6	46.2
Total telecommunications services revenue									$ 42.8	$ 46.2	$ 14.1