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, 2020 USD ($) buildings	Dec. 31, 2019 USD ($)
Discontinued Operations
Continuing Operations, Number of In-service Properties Held for Sale | buildings	2
Land and Land Improvements Held-for-Sale	$ 27,954
Buildings and Tenant Improvements Held-for-Sale	44,800
Accumulated Depreciation of Assets Held-for-Sale	(5,976)
Total assets held-for-sale	67,946	$ 18,463
Total liabilities held-for-sale	7,740	887
Continuing Operations [Member]
Discontinued Operations
Land and Land Improvements Held-for-Sale	27,954	4,561
Buildings and Tenant Improvements Held-for-Sale	44,800	18,840
Accumulated Depreciation of Assets Held-for-Sale	(5,976)	(7,132)
Lease Related Assets, Held for Sale	936	2,100
Other assets	232	94
Total assets held-for-sale	67,946	18,463
Accrued Expenses Held-for-Sale	660	643
Other Liabilities Held-for-Sale	7,080	244
Total liabilities held-for-sale	$ 7,740	$ 887