Real Estate Facilities (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) ft² storageFacility	Sep. 30, 2020 USD ($)
Schedule Of Real Estate Facilities [Line Items]
Increase (decrease) in accrued unpaid construction costs			$ 7,400	$ 2,900
Increase (decrease) in accrued capital expenditures to maintain real estate facilities			7,900	(6,900)
Proceeds from sale of real estate investments			16,070	1,399
Gain on sale of real estate	$ 279	$ 0	13,683	$ 1,117
Disposal of Real Estate Facilities
Schedule Of Real Estate Facilities [Line Items]
Gain on sale of real estate			$ 13,700
Acquisition Of Self-Storage Facilities Other Investments
Schedule Of Real Estate Facilities [Line Items]
Number of operating self-storage facilities | storageFacility			126
Net rentable area acquired | ft²			10,295,000
Total cost of acquisition			$ 2,800,000
Payments to acquire intangible assets			103,300
Newly Developed and Expansion Projects | Completed Developed and Expansion Project
Schedule Of Real Estate Facilities [Line Items]
Aggregate costs to develop and expand			$ 171,100
Addtional net rentable square feet | ft²			1,200,000