REAL ESTATE AND OTHER AFFILIATES (Narrative) (Details)			1 Months Ended	3 Months Ended		12 Months Ended
	Jun. 01, 2016 ft²	Oct. 04, 2013 USD ($) a	Jan. 31, 2016 USD ($) extention_option	Jun. 30, 2018 USD ($)	Mar. 31, 2015 USD ($) item	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)
Real Estate and Other Affiliates
Investment in Real Estate and Other Affiliates						$ 102,287,000	$ 76,593,000
Number of variable interest entities in which entity is primary beneficiary | item						6
Carrying values of the assets associated with the operations of the consolidated VIEs						$ 190,600,000	24,800,000
Carrying values of the liabilities associated with the operations of the consolidated VIEs						$ 99,800,000	$ 2,700,000
Number of business segment | item						3
Acquisition of 1% partnership interest in 110 North Wacker						1.00%	1.00%	1.00%
Equity in earnings from Real Estate and Other Affiliates						$ 39,954,000	$ 25,498,000	$ 56,818,000
USAA Joint Venture
Real Estate and Other Affiliates
Fair value of the land contributed to joint venture				$ 33,600,000
Contribution of property				85,000,000
Joint venture capital obligations				$ 42,700,000
Joint venture agreement, equity ownership percentage				33.00%
Joint venture, preferred return on capital				9.00%
Acquisition of 1% partnership interest in 110 North Wacker						90.00%
USAA Joint Venture | USAA
Real Estate and Other Affiliates
Capital contribution				$ 64,000,000
Joint venture capital obligations				$ 105,600,000
Joint venture, preferred return on capital				9.00%
Joint venture, preferred return on capital, percent of cash distributions				11.11%
Acquisition of 1% partnership interest in 110 North Wacker						10.00%
The Summit
Real Estate and Other Affiliates
Preferred return, on capital (as a percent)					5.00%
Entitlement of distribution by joint venture (in times) | item					2
Circle T Ranch and Power Center
Real Estate and Other Affiliates
Area of land sold | ft²	72
Equity in earnings from Real Estate and Other Affiliates								10,500,000
m.flats/TEN.M
Real Estate and Other Affiliates
Fair value of the land contributed to joint venture		$ 4,000,000
Transaction value of the land contributed to joint venture		$ 23,400,000
Area of land contributed to the joint venture (in acres) | a		5
Additional capitalized development costs incurred resulting from contribution of land		$ 3,100,000
Total book value contribution		7,100,000
Transaction value, per constructed unit of land contributed to joint venture		$ 53,500
Distribution of the cash contributed by joint venture partner			$ 7,300,000
Contribution made till date								6,300,000
Gain recognized on the sale of Redlands Promenade								200,000
m.flats/TEN.M | Kettler Inc
Real Estate and Other Affiliates
Amount funded in cash to joint venture			16,100,000
m.flats/TEN.M | Construction Loan Payable
Real Estate and Other Affiliates
Non-recourse construction loan			$ 88,000,000
Number of extension options | extention_option			3
Option to extend, term			1 year
33 Peck Slip
Real Estate and Other Affiliates
Capital contribution			$ 6,000,000
Amount funded in cash to joint venture							700,000	2,300,000
33 Peck Slip | Bridge Loan
Real Estate and Other Affiliates
Interest rate margin (as a percent)			5.00%
Amount of bridge loan			$ 25,000,000
33 Peck Slip | Construction Loan Payable
Real Estate and Other Affiliates
Redevelopment loan									$ 36,000,000
Equity Method Investments | The Summit
Real Estate and Other Affiliates
Fair value of the land contributed to joint venture					$ 13,400,000
SID Bonds transferred to a joint venture					1,300,000
Transaction value of the land contributed to joint venture					125,400,000
Value of land contributed to joint venture, price per acre					226,000
Maximum capital contribution required					$ 30,000,000.0
One Month LIBOR
Real Estate and Other Affiliates
Interest rate margin (as a percent)						2.5027%
One Month LIBOR | m.flats/TEN.M | Construction Loan Payable
Real Estate and Other Affiliates
Interest rate margin (as a percent)			2.40%
Operating Assets | Equity Method Investments | Mr. C Seaport
Real Estate and Other Affiliates
Investment in Real Estate and Other Affiliates						$ 8,721,000	0
Equity in earnings from Real Estate and Other Affiliates						(465,000)	0	0
Operating Assets | Equity Method Investments | m.flats/TEN.M
Real Estate and Other Affiliates
Investment in Real Estate and Other Affiliates						4,701,000	0
Equity in earnings from Real Estate and Other Affiliates						(2,478,000)	$ 0	$ 0
Unconsolidated Properties
Real Estate and Other Affiliates
Secured debt						201,500,000
Share of the entity in secured debt						$ 96,200,000
110 N Wacker | Operating Assets
Real Estate and Other Affiliates
Recourse percentage						18.00%
Facility amount						$ 9,000,000