Organization and Principles of Consolidation Revenues and Tenant and Other Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Management, transaction, and other fee [Member]
Schedule of management, transaction, and other fees [Line Items]
Accounts Receivable, Net	$ 10,100		$ 10,100
Parent Company [Member]
Schedule of management, transaction, and other fees [Line Items]
Property Management Fee Revenue	6,954	$ 6,047	20,999	$ 19,353
Accounts Receivable, Net	160,709		160,709		$ 170,985
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					30,903
Parent Company [Member] | Property management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Property Management Fee Revenue	3,588	3,446	11,008	10,452
Parent Company [Member] | Asset management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Property Management Fee Revenue	1,840	1,762	5,347	5,314
Parent Company [Member] | Leasing services [Member]
Schedule of management, transaction, and other fees [Line Items]
Property Management Fee Revenue	969	669	2,726	2,285
Parent Company [Member] | Other transaction fees [Member]
Schedule of management, transaction, and other fees [Line Items]
Property Management Fee Revenue	557	$ 170	1,918	$ 1,302
Parent Company [Member] | Management, transaction, and other fee [Member]
Schedule of management, transaction, and other fees [Line Items]
Accounts Receivable, Net					$ 8,700
Accounting Standards Update 2017-05 [Member]
Schedule of management, transaction, and other fees [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 30,900		$ 30,900