REAL ESTATE EQUITY SECURITIES (Shares Owned) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Total Carrying Value	$ 81,439	$ 73,876
Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Number of Shares Owned (in shares)	67,354,922	61,533,775
Whitestone REIT
Schedule of Available-for-sale Securities [Line Items]
Total Carrying Value	$ 0	$ 21,846
Whitestone REIT | Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Number of Shares Owned (in shares)	0	1,781,894
Keppel Pacific Oak US REIT
Schedule of Available-for-sale Securities [Line Items]
Total Carrying Value	$ 50,049	$ 34,757
Keppel Pacific Oak US REIT | Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Number of Shares Owned (in shares)	64,165,352	56,979,352
Franklin Street Properties Corp.
Schedule of Available-for-sale Securities [Line Items]
Total Carrying Value	$ 23,743	$ 17,273
Franklin Street Properties Corp. | Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Number of Shares Owned (in shares)	2,773,729	2,772,529
Plymouth Industrial REIT, Inc.
Schedule of Available-for-sale Securities [Line Items]
Total Carrying Value	$ 7,647	$ 0
Plymouth Industrial REIT, Inc. | Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Number of Shares Owned (in shares)	415,841	0