Schedule III - Schedule of Real Estate and Accumulated Depreciation (Schedule of Real Estate and Accumulated Depreciation) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) item site	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Description | site	34,177
Encumbrances	$ 9,396,000
Gross Amount Carried at Close of Current Period	7,068,208	$ 5,963,048	$ 5,833,338	$ 5,561,005
Accumulated Depreciation at Close of Current Period	$ (3,644,238)	$ (3,383,370)	$ (3,133,061)	$ (2,868,507)
Date of Construction	Various
Date Acquired	Various
Secured debt	$ 9,400,000
Maximum [Member]
Life on Which Depreciation in Latest Income Statement is Computed	70 years
Exclusive Right to Lease and Operate Utility Transmission Structures [Member]
Number of utility transmission structures acquired | item	713
Product Concentration Risk [Member] | Minimum [Member] | Real Estate, Gross [Member] | Sites [Member]
Concentration risk percentage	5.00%