Schedule III - Schedule of Real Estate and Accumulated Depreciation (Reconciliation of Real Estate Accumulated Depreciation) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) item	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Gross amount of accumulated depreciation at beginning	$ (3,383,370)	$ (3,133,061)	$ (2,868,507)
Depreciation	(273,655)	(275,947)	(269,606)
Other	(91)	(38)	(83)
Total additions	(273,746)	(275,985)	(269,689)
Amount of accumulated depreciation for assets sold or disposed	3,638	4,244	2,887
Other	9,240	21,432	2,248
Total deductions	12,878	25,676	5,135
Balance at end	$ (3,644,238)	$ (3,383,370)	$ (3,133,061)
Exclusive Right to Lease and Operate Utility Transmission Structures [Member]
Number of utility transmission structures acquired | item	713