GOODWILL AND OTHER INTANGIBLE ASSETS - INTANGIBLE ASSETS SUBJECT TO AMORTIZATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 17,254.1	$ 17,931.6
Accumulated Amortization	(5,653.5)	(5,613.2)
Net Book Value	11,600.6	12,318.4
Acquired network location intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,967.0	5,150.8
Accumulated Amortization	(1,938.8)	(1,920.4)
Net Book Value	$ 3,028.2	3,230.4
Acquired network location intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	20 years
Acquired tenant-related intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 12,193.2	12,674.1
Accumulated Amortization	(3,707.5)	(3,674.6)
Net Book Value	$ 8,485.7	8,999.5
Acquired tenant-related intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	20 years
Acquired licenses and other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 93.9	106.7
Accumulated Amortization	(7.2)	(18.2)
Net Book Value	$ 86.7	$ 88.5
Acquired licenses and other intangibles | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	3 years
Acquired licenses and other intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Lives (years)	20 years