REAL ESTATE HELD FOR INVESTMENT (Narrative) (Details) ft² in Millions	Sep. 30, 2018 a ft² unit property investment
Real Estate Properties [Line Items]
Rentable square feet | ft²	3.8
Percentage of portfolio occupied	76.00%
Office Properties
Real Estate Properties [Line Items]
Number of real estate properties	6
Undeveloped Land, Portfolio
Real Estate Properties [Line Items]
Real estate area of undeveloped land | a	14
Office/Flex/Industrial Portfolio
Real Estate Properties [Line Items]
Number of real estate properties	1
Office/Flex/Industrial Buildings
Real Estate Properties [Line Items]
Number of real estate properties	21
Retail Property, Portfolio
Real Estate Properties [Line Items]
Number of real estate properties	1
Apartment Property
Real Estate Properties [Line Items]
Number of real estate properties	2
Apartment Building
Real Estate Properties [Line Items]
Rentable square feet | ft²	0.3
Percentage of portfolio occupied	94.00%
Number of units in real estate property | unit	383
Undeveloped Land
Real Estate Properties [Line Items]
Real estate area of undeveloped land | a	1,000
Number of investments in real estate | investment	3