REAL ESTATE EQUITY SECURITIES - Shares Owned (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Number of Shares Owned (in shares)	69,144,899	67,354,922
Total Carrying Value	$ 64,024	$ 81,439
Kepple Pacific Oak US REIT
Debt Securities, Available-for-sale [Line Items]
Number of Shares Owned (in shares)	64,165,352	64,165,352
Total Carrying Value	$ 32,403	$ 50,049
Franklin Street Properties Corp.
Debt Securities, Available-for-sale [Line Items]
Number of Shares Owned (in shares)	4,410,824	2,773,729
Total Carrying Value	$ 25,274	$ 23,743
Plymouth Industrial REIT, Inc.
Debt Securities, Available-for-sale [Line Items]
Number of Shares Owned (in shares)	568,723	415,841
Total Carrying Value	$ 6,347	$ 7,647