Organization and Significant Accounting Policies - Revenues and Tenant and Other Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Schedule of management, transaction, and other fees [Line Items]
Other property income	$ 2,435	$ 2,194	$ 4,740	$ 4,176
Management, transaction, and other fees	6,126	7,442	12,942	14,415
Tenant and other receivables	186,232		186,232		$ 169,337
Management, transaction, and other fee [Member]
Schedule of management, transaction, and other fees [Line Items]
Tenant and other receivables	9,200		9,200		$ 11,600
Property management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	3,353	3,665	7,232	7,428
Asset management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	1,756	1,760	3,594	3,538
Leasing services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	529	705	1,239	1,463
Other transaction fees [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	$ 488	$ 1,312	$ 877	$ 1,986