Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset	$ 14,600,000
Operating lease, right-of-use liability	14,417,000
Operating lease cost	700,000
Total revenues	36,883,000	$ 37,568,000
Adjustment to opening equity prior period	500,000
Rents [Member] | Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Total revenues		28,200,000
Expense Recoveries [Member] | Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Total revenues		$ 9,300,000
Accounts Payable and Accrued Liabilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use liability	$ 14,600,000