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	6 Months Ended
	Jun. 30, 2020 USD ($) buildings	Dec. 31, 2019 USD ($)
Held for Sale Assets in Continuing and Discontinued Operations
Continuing Operations, Number of In-service Properties Held for Sale | buildings	0
Total assets held-for-sale	$ 0	$ 18,463
Total liabilities held-for-sale	0	887
Continuing Operations [Member]
Held for Sale Assets in Continuing and Discontinued Operations
Land and Land Improvements Held-for-Sale	0	4,561
Buildings and Tenant Improvements Held-for-Sale	0	18,840
Inventory, Land Held-for-sale	0	0
Accumulated Depreciation of Assets Held-for-Sale	0	(7,132)
Deferred leasing and other costs, net	0	2,100
Other assets	0	94
Total assets held-for-sale	0	18,463
Total liabilities held-for-sale	$ 0	$ 887