Organization and Principles of Consolidation Revenues and Tenant and Other Receivables (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) ft²	Sep. 30, 2018 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Schedule of management, transaction, and other fees [Line Items]
Lease liabilities	$ 223,581		$ 223,581		$ 225,400	$ 0
Right of use assets, net	294,051		294,051		$ 297,800	0
Other property income	2,780	$ 2,408	6,956	$ 6,755
Management, transaction, and other fees	7,353	6,954	21,768	20,999
Tenant and other receivables	161,381		161,381			172,359
Management, transaction, and other fee [Member]
Schedule of management, transaction, and other fees [Line Items]
Tenant and other receivables	11,100		11,100			$ 12,500
Property management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	3,648	3,588	11,076	11,008
Asset management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	1,803	1,840	5,341	5,347
Leasing services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	1,239	969	2,702	2,726
Other transaction fees [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	$ 663	$ 557	$ 2,649	$ 1,918
Leases less than 10,000 sqft [Member]
Schedule of management, transaction, and other fees [Line Items]
Operating leases, tenant space terms | ft²			10,000
Leases greater then 10,000sqft [Member]
Schedule of management, transaction, and other fees [Line Items]
Operating leases, tenant space terms | ft²			10,000
Minimum [Member]
Schedule of management, transaction, and other fees [Line Items]
Operating leases, lease year range			3 years
Operating leases, lease year range for tenant space greater than 10,000 sq ft			5 years
Maximum [Member]
Schedule of management, transaction, and other fees [Line Items]
Operating leases, lease year range			7 years