REAL ESTATE AND OTHER AFFILIATES (Summary of Investments in Real Estate and Other Affiliates) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Investment in Real Estate and Other Affiliates
Carrying Value	$ 121,611		$ 121,611		$ 102,287
Share of Earnings/Dividends	4,542	$ 8,612	20,847	$ 39,297
Cost method investments
Investment in Real Estate and Other Affiliates
Carrying Value	3,952		3,952		3,856
Share of Earnings/Dividends	0	0	3,625	3,341
Accounts payable and accrued expenses | The Metropolitan Downtown Columbia
Investment in Real Estate and Other Affiliates
Investment deficit position	$ 4,000		$ 4,000		$ 3,800
Operating Assets | The Metropolitan Downtown Columbia | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	50.00%		50.00%		50.00%
Carrying Value	$ 0		$ 0		$ 0
Share of Earnings/Dividends	$ 172	87	$ 478	371
Operating Assets | Stewart Title of Montgomery County, TX | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	50.00%		50.00%		50.00%
Carrying Value	$ 3,899		$ 3,899		$ 3,920
Share of Earnings/Dividends	$ 306	165	$ 579	393
Operating Assets | Woodlands Sarofim 1 | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	20.00%		20.00%		20.00%
Carrying Value	$ 2,849		$ 2,849		$ 2,760
Share of Earnings/Dividends	$ 38	30	$ 89	66
Operating Assets | m.flats/TEN.M | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	50.00%		50.00%		50.00%
Carrying Value	$ 3,132		$ 3,132		$ 4,701
Share of Earnings/Dividends	$ (75)	(357)	$ (1,576)	(2,661)
Master Planned Communities | The Summit | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	0.00%		0.00%		0.00%
Carrying Value	$ 86,969		$ 86,969		$ 72,171
Share of Earnings/Dividends	$ 4,523	9,454	$ 18,859	34,682
Seaport District | Mr. C Seaport | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	35.00%		35.00%		35.00%
Carrying Value	$ 8,002		$ 8,002		$ 8,721
Share of Earnings/Dividends	$ (545)	(452)	$ (1,628)	(452)
Seaport District | Bar Wayo (Momofuku) | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	0.00%		0.00%		0.00%
Carrying Value	$ 6,070		$ 6,070		$ 0
Share of Earnings/Dividends	(160)	0	(160)	0
Strategic Developments | Equity Method Investments
Investment in Real Estate and Other Affiliates
Carrying Value	117,659		117,659		$ 98,431
Share of Earnings/Dividends	$ 4,542	8,612	$ 17,222	35,956
Strategic Developments | Mr. C Seaport | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	35.00%		35.00%		35.00%
Carrying Value	$ 0		$ 0		$ 0
Share of Earnings/Dividends	$ 0	0	$ 0	(240)
Strategic Developments | Circle T Ranch and Power Center | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	50.00%		50.00%		50.00%
Carrying Value	$ 6,680		$ 6,680		$ 5,989
Share of Earnings/Dividends	$ 400	(318)	$ 691	3,118
Strategic Developments | HHMK Development | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	50.00%		50.00%		50.00%
Carrying Value	$ 10		$ 10		$ 10
Share of Earnings/Dividends	$ 0	0	$ 0	0
Strategic Developments | KR Holdings | Equity Method Investments
Investment in Real Estate and Other Affiliates
Economic/Legal Ownership	50.00%		50.00%		50.00%
Carrying Value	$ 48		$ 48		$ 159
Share of Earnings/Dividends	$ (117)	$ 3	$ (110)	$ 679