Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies [Line Items]
Gain (loss) on sale of investments	$ 0	$ 0
Long-term investments	57,600,000	13,300,000
Interest cost capitalized	$ 600,000	700,000	$ 900,000
Intangible assets, useful life	15 years
Impairment charge recognized, related to long-lived assets	$ 40,100,000	33,100,000	27,100,000
Asset retirement obligation	30,900,000	11,500,000
Accounts receivable, net	74,088,000	132,125,000
Unamortized deferred lease costs	1,200,000	1,800,000
Amortization expense	1,300,000	1,400,000
Deferred lease costs	4,800,000	4,900,000
Gain (loss) on remeasurement of U.S. dollar denominated intercompany loan	(145,600,000)	9,000,000.0	$ (58,800,000)
Intercompany foreign currency outstanding balance	$ 909,800,000	899,700,000
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Acquired intangible assets, useful life	1 year
Fixed rent escalation	2.00%
Lease term	5 years
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Business acquistions period after closing date to determine additional adjustments	1 year
Acquired intangible assets, useful life	3 years
Fixed rent escalation	3.00%
Lease term	10 years
Domestic Site Leasing [Member] | Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Concentration risk percentage	94.00%
Site Development Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Accounts receivable, net	$ 14,300,000	$ 40,700,000
Site Development Revenue [Member] | Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Concentration risk percentage	6.00%