LEASES -Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) renewalOption tenant	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Lessor, Lease, Description [Line Items]
Number of tenants | tenant	1
Operating lease, number of renewal options | renewalOption	1
Impairment charges	$ 222,800,000	$ 94,200,000	$ 394,000,000.0
Interest expense on finance lease liabilities	1,300,000	1,700,000
Lease Agreements
Lessor, Lease, Description [Line Items]
Impairment charges	$ 76,100,000	$ 9,900,000
Minimum
Lessor, Lease, Description [Line Items]
Lessor, term of lease	5 years
Operating lease, term of contract	5 years
Maximum
Lessor, Lease, Description [Line Items]
Lessor, term of lease	10 years
Estimated useful lives	20 years
Operating lease, term of contract	10 years
Maximum | Towers
Lessor, Lease, Description [Line Items]
Estimated useful lives	20 years
Maximum | Communication Sites
Lessor, Lease, Description [Line Items]
Estimated useful lives	20 years