SEGMENT REPORTING - Capital Expenditures (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 14,441	$ 23,980	$ 53,574	$ 74,441
Office
Segment Reporting Information [Line Items]
Capital expenditures	[1]	12,572	16,548	40,053	50,449
Retail
Segment Reporting Information [Line Items]
Capital expenditures	[1]	747	5,290	7,110	16,731
Multifamily
Segment Reporting Information [Line Items]
Capital expenditures	[1]	800	1,297	2,944	2,753
Mixed-use
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 322	$ 845	$ 3,467	$ 4,508

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