SEGMENT REPORTING - Capital Expenditures (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 28,024	$ 12,045	$ 50,461	$ 23,410
Retail
Segment Reporting Information [Line Items]
Capital expenditures	[1]	6,650	3,228	11,441	5,457
Office
Segment Reporting Information [Line Items]
Capital expenditures	[1]	17,418	7,513	33,901	14,886
Multifamily
Segment Reporting Information [Line Items]
Capital expenditures	[1]	685	875	1,456	2,484
Mixed-Use
Segment Reporting Information [Line Items]
Capital expenditures	[1]	$ 3,271	$ 429	$ 3,663	$ 583

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