Related Party Transactions (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Interest and other income	$ 764,000	$ 294,000	$ 1,382,000	$ 578,000
Royalty-free license agreement written notice of termination period minimum (in months)			6 months
Number of assets owned that are maintained by Public Storage | item	2		2
Property management contract written notice of termination period minimum (in days)			60 days
Management fee expenses	$ 25,000	24,000	$ 49,000	47,000
Costs allocated from related party	19,000	18,000	37,000	35,000
Reimbursement to related party	168,000	409,000	420,000	639,000
Reimbursement from related party	9,000	10,000	17,000	19,000
Due to related parties	127,000		127,000
Due from related parties					$ 43,000
Property Management [Member]
Related Party Transaction [Line Items]
Interest and other income	72,000	112,000	150,000	238,000
Operating expenses allocated to operating party	$ 91,000	$ 121,000	$ 193,000	$ 275,000