Real Estate Facilities (Activity In Real Estate Facilities) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) ft²	Dec. 31, 2018 USD ($) ft²
Property, Plant and Equipment [Line Items]
Beginning Balances	$ 1,822,390
Accumulated Depreciation, Beginning Balances	(1,097,748)
Acquisition of real estate facility	13,646
Capital expenditures	17,722
Depreciation and amortization expense	(48,598)
Transfer to properties held for sale	3,413
Accumulated Depreciation, Ending Balances	(1,135,107)
Ending Balances	1,808,573
Properties held for sale, net	$ 124,680	$ 128,093
Area of real estate property (in square feet) | ft²	628,000
Properties Held for Sale or Sold [Member]
Property, Plant and Equipment [Line Items]
Area of real estate property (in square feet) | ft²	1,300,000	1,300,000
Land [Member]
Property, Plant and Equipment [Line Items]
Beginning Balances	$ 762,731
Acquisition of real estate facility	9,668
Ending Balances	772,399
Buildings And Improvements [Member]
Property, Plant and Equipment [Line Items]
Beginning Balances	2,157,407
Acquisition of real estate facility	3,978
Capital expenditures	17,722
Disposals	(7,184)
Transfer to properties held for sale	(642)
Ending Balances	2,171,281
Accumulated Depreciation [Member]
Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Beginning Balances	(1,097,748)
Accumulated Depreciation, Disposals	7,184
Depreciation and amortization expense	(48,598)
Transfer to properties held for sale	4,055
Accumulated Depreciation, Ending Balances	(1,135,107)
Reclassification [Member]
Property, Plant and Equipment [Line Items]
Beginning Balances	(128,100)
Properties held for sale, net		$ 128,100
Reclassification [Member] | Land [Member]
Property, Plant and Equipment [Line Items]
Beginning Balances	(53,900)
Properties held for sale, net		53,900
Reclassification [Member] | Buildings And Improvements [Member]
Property, Plant and Equipment [Line Items]
Beginning Balances	(217,500)
Properties held for sale, net		217,500
Reclassification [Member] | Accumulated Depreciation [Member]
Property, Plant and Equipment [Line Items]
Beginning Balances	$ (143,300)
Properties held for sale, net		$ 143,300