REAL ESTATE AND OTHER AFFILIATES (Narrative) (Details)		3 Months Ended			12 Months Ended
	May 23, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2016	Mar. 31, 2015 USD ($) item	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Real Estate and Other Affiliates
Number of variable interest entities in which entity is primary beneficiary | item					1
Recourse percentage					100.00%
Carrying values of the assets associated with the operations of the consolidated VIEs					$ 393,300,000	$ 190,600,000
Carrying values of the liabilities associated with the operations of the consolidated VIEs					$ 186,500,000	99,800,000
Capital contribution	$ 178,400,000
Joint venture capital obligations	$ 8,800,000
Bar Wayo
Real Estate and Other Affiliates
Joint venture, preferred return on capital, percent of cash distributions			75.00%
Preferred return, on capital (as a percent)			10.00%
Joint venture real estate, percentage funded			89.75%
Join venture real estate, remaining cash distribution percentage			50.00%
USAA Joint Venture
Real Estate and Other Affiliates
Fair value of the land contributed to joint venture		$ 33,600,000
Contribution of property		85,000,000.0
Joint venture capital obligations		$ 42,700,000
Joint venture agreement, equity ownership percentage		23.00%
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		$ 64,000,000.0
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
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
Operating Assets revenues | Bar Wayo
Real Estate and Other Affiliates
Investment in real estate and other affiliates						0
Operating Assets revenues | Equity Method Investments | Mr. C Seaport
Real Estate and Other Affiliates
Investment in real estate and other affiliates					$ 7,650,000	8,721,000
Operating Assets revenues | Equity Method Investments | Bar Wayo
Real Estate and Other Affiliates
Investment in real estate and other affiliates					7,469,000
Operating Assets revenues | Equity Method Investments | m.flats/TEN.M
Real Estate and Other Affiliates
Investment in real estate and other affiliates					2,431,000	$ 4,701,000
Unconsolidated Properties
Real Estate and Other Affiliates
Secured debt					209,400,000
Share of the entity in secured debt					$ 100,300,000
Momofuku | Bar Wayo
Real Estate and Other Affiliates
Joint venture, preferred return on capital, percent of cash distributions			25.00%
Joint venture real estate, percentage funded			10.25%