Discontinued Operations and Assets Held for Sale (Aggregate Balance Sheet of Properties Held for Sale Included in Discontinued Operations) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) a buildings	Dec. 31, 2015 USD ($)
Discontinued Operations
Discontinued Operation, Number of Real Estate Properties Held for Sale | buildings	0
Continuing Operations, Number of In-service Properties Held for Sale | buildings	5
Land and Land Improvements Held-for-Sale	$ (3,631)
Buildings and Tenant Improvements Held-for-Sale	(37,495)
Accumulated Depreciation of Assets Held-for-Sale	18,581
Total assets held-for-sale	51,627	$ 45,801
Total liabilities held-for-sale	$ 1,661	972
Area of Land | a	39
Continuing Operations [Member]
Discontinued Operations
Land and Land Improvements Held-for-Sale	$ 3,631	9,797
Buildings and Tenant Improvements Held-for-Sale	37,495	39,480
Inventory, Land Held-for-sale	22,657	0
Accumulated Depreciation of Assets Held-for-Sale	(18,581)	(7,183)
Lease Related Assets, Held for Sale	3,091	3,293
Other assets	3,334	414
Total assets held-for-sale	51,627	45,801
Accrued expenses	1,363	322
Other liabilities	298	650
Total liabilities held-for-sale	$ 1,661	$ 972