SEGMENT REPORTING - Capital Expenditures (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 21,743	$ 14,441	$ 58,797	$ 53,574
Office
Segment Reporting Information [Line Items]
Capital expenditures	[1]	17,601	12,572	48,471	40,053
Retail
Segment Reporting Information [Line Items]
Capital expenditures	[1]	1,317	747	4,817	7,110
Multifamily
Segment Reporting Information [Line Items]
Capital expenditures	[1]	2,121	800	4,117	2,944
Mixed-use
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 704	$ 322	$ 1,392	$ 3,467

[1] Capital expenditures represent cash paid for capital expenditures during the period and include leasing commissions paid