SEGMENT REPORTING - Capital Expenditures (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Capital Expenditures	[1]	$ 46,542	$ 31,593	$ 91,510	$ 62,889
Total Retail
Segment Reporting Information [Line Items]
Capital Expenditures	[1]	1,756	1,125	2,691	2,631
Total Office
Segment Reporting Information [Line Items]
Capital Expenditures	[1]	14,872	8,590	29,586	15,681
Total Multifamily
Segment Reporting Information [Line Items]
Capital Expenditures	[1]	29,748	19,763	58,696	41,640
Total Mixed-Use
Segment Reporting Information [Line Items]
Capital Expenditures	[1]	$ 166	$ 2,115	$ 537	$ 2,937

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