Other Assets and Deferred Charges, Net (Components of Other Assets and Deferred Charges, Net) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Deferred Costs And Other Assets [Line Items]
Lease origination costs	$ 22,331,000	$ 19,947,000
Right-of-use assets	13,828,000	13,638,000	$ 14,600,000
Prepaid expenses	6,906,000	6,048,000
Investments related to share-based compensation	948,000	823,000
Unsecured revolving credit facility financing costs	2,002,000	2,769,000
Leasehold improvements, furniture and fixtures	85,000	200,000
Interest rate swaps		136,000
Other	534,000	326,000
Total other assets and deferred charges, net	45,255,000	42,139,000
Intangible Lease Assets [Member]
Deferred Costs And Other Assets [Line Items]
Deferred charges, net	5,500,000	6,600,000
Cost of intangible lease assets	19,400,000	19,900,000
Accumulated amortization of intangible lease assets	13,900,000	13,300,000
Unsecured Revolving Credit Facility [Member]
Deferred Costs And Other Assets [Line Items]
Unsecured revolving credit facility financing costs	623,000	$ 1,021,000
Accumulated amortization of intangible lease assets	$ 37,100,000