Real Estate Assets, Discontinued Operations and Assets Held for Sale (Aggregate Balance Sheet of Properties Held for Sale Included in Discontinued Operations) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) buildings	Dec. 31, 2018 USD ($)
Held for Sale Assets in Continuing and Discontinued Operations
Continuing Operations, Number of In-service Properties Held for Sale | buildings	0
Number of Real Estate Properties Held for Sale | buildings	0
Total assets held-for-sale	$ 1,940	$ 1,082
Total liabilities held-for-sale	41	0
Continuing Operations [Member]
Held for Sale Assets in Continuing and Discontinued Operations
Land and Land Improvements Held-for-Sale	1,989	0
Buildings and Tenant Improvements Held-for-Sale	855	0
Inventory, Land Held-for-sale	0	1,966
Accumulated Depreciation of Assets Held-for-Sale	(1,025)	(884)
Deferred leasing and other costs, net	42	0
Other assets	79	0
Total assets held-for-sale	1,940	1,082
Total liabilities held-for-sale	$ 41	$ 0