Organization and Principles of Consolidation Revenues and Tenant and Other Receivables (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) ft²	Jun. 30, 2018 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Schedule of management, transaction, and other fees [Line Items]
Lease liabilities	$ 223,959		$ 223,959		$ 225,400	$ 0
Right of use assets, net	295,084		295,084		$ 297,800	0
Other property income	2,194	$ 2,322	4,176	$ 4,347
Management, transaction, and other fees	7,442	6,887	14,415	14,045
Tenant and other receivables	157,883		157,883			172,359
Management, transaction, and other fee [Member]
Schedule of management, transaction, and other fees [Line Items]
Tenant and other receivables	11,000		11,000			$ 12,500
Property management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	3,665	3,652	7,428	7,420
Asset management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	1,760	1,804	3,538	3,507
Leasing services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	705	1,072	1,463	1,757
Other transaction fees [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	$ 1,312	$ 359	$ 1,986	$ 1,361
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