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, 2018 USD ($) a buildings	Dec. 31, 2017 USD ($)
Held for Sale Assets in Continuing and Discontinued Operations
Number of Real Estate Properties Held for Sale | buildings	2
Area of Land | a	10
Total assets held-for-sale	$ 21,740	$ 17,550
Total liabilities held-for-sale	1,327	1,163
Continuing Operations [Member]
Held for Sale Assets in Continuing and Discontinued Operations
Land and Land Improvements Held-for-Sale	9,055	8,157
Buildings and Tenant Improvements Held-for-Sale	15,283	10,505
Inventory, Land Held-for-sale	706	0
Accumulated Depreciation of Assets Held-for-Sale	(4,824)	(2,553)
Lease Related Assets, Held for Sale	862	862
Other assets	658	579
Total assets held-for-sale	21,740	17,550
Total liabilities held-for-sale	$ 1,327	$ 1,163