Revenues (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Lessor Lease Description [Line Items]
Payment accepted on termination of lease prior to contractual expiration	$ 4,300,000
Total revenues		$ 41,350,000	$ 35,699,000	$ 78,918,000	$ 72,473,000
Contract Termination [Member]
Lessor Lease Description [Line Items]
Total revenues		5,400,000		5,400,000
Cash payment reduced by straight line rent receivable		500,000		500,000
Accelerated Intangible Lease Amortization [Member] | Contract Termination [Member]
Lessor Lease Description [Line Items]
Total revenues		1,500,000		1,500,000
Other Income [Member] | Contract Termination [Member]
Lessor Lease Description [Line Items]
Total revenues		$ 3,800,000		$ 3,800,000