Noncontrolling Interests (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) item	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) item shares	Jun. 30, 2019 USD ($)
Noncontrolling Interest [Line Items]
Distributions paid	$ 1,378	$ 1,730	$ 2,550	$ 3,533
Contributions by noncontrolling interests	$ 867	1,106	$ 1,433	1,302
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Permanent noncontrolling interest in subsidiaries, number of self-storage facilities | item	20		20
Permanent noncontrolling interest in subsidiaries, number of self-storage facilities under construction | item			6
Partnership units conversion ratio			1
Convertible partnership units | shares			231,978
Income allocated to other permanent noncontrolling interest in subsidiaries			$ 1,900	2,600
Distributions paid	$ 1,378	1,730	2,550	3,533
Contributions by noncontrolling interests	$ 867	$ 1,106	$ 1,433	$ 1,302