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	9 Months Ended
	Sep. 30, 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	1
Total assets held-for-sale	$ 23,739	$ 1,082
Total liabilities held-for-sale	2,515	0
Continuing Operations [Member]
Held for Sale Assets in Continuing and Discontinued Operations
Land and Land Improvements Held-for-Sale	1,268	0
Buildings and Tenant Improvements Held-for-Sale	26,879	0
Inventory, Land Held-for-sale	0	1,966
Accumulated Depreciation of Assets Held-for-Sale	(7,931)	(884)
Deferred leasing and other costs, net	3,057	0
Other assets	466	0
Total assets held-for-sale	23,739	1,082
Disposal Group, Including Discontinued Operation, Accrued Liabilities	761	0
Disposal Group, Including Discontinued Operation, Other Liabilities	1,754	0
Total liabilities held-for-sale	$ 2,515	$ 0