Organization and Significant Accounting Policies - Revenues and Tenant and Other Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	$ 7,355	$ 6,126	$ 13,748	$ 12,942
Tenant and other receivables	131,510		131,510		$ 143,633
Management, transaction, and other fee [Member]
Schedule of management, transaction, and other fees [Line Items]
Tenant and other receivables	12,000		12,000		$ 9,900
Property management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	3,753	3,353	7,524	7,232
Asset management services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	1,719	1,756	3,434	3,594
Leasing services [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	1,336	529	2,187	1,239
Other transaction fees [Member]
Schedule of management, transaction, and other fees [Line Items]
Management, transaction, and other fees	$ 547	$ 488	$ 603	$ 877