Schedule III - Schedule of Real Estate and Accumulated Depreciation (Schedule of Real Estate and Accumulated Depreciation) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) site	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Description | site	32,403
Encumbrances	$ 7,814,000
Gross Amount Carried at Close of Current Period	5,833,338	$ 5,561,005	$ 5,340,858	$ 5,079,660
Accumulated Depreciation at Close of Current Period	$ (3,133,061)	$ (2,868,507)	$ (2,627,841)	$ (2,396,587)
Date of Construction	Various
Date Acquired	Various
Secured debt	$ 7,800,000
Maximum [Member]
Life on Which Depreciation in Latest Income Statement is Computed	20 years
Minimum [Member] | Real Estate, Gross [Member]
Concentration risk percentage	5.00%