REAL ESTATE - Disposition (Details) $ in Millions	Jan. 23, 2020 USD ($)	Jan. 22, 2020 USD ($)	Oct. 10, 2008 ft² a numberOfProperties	Sep. 09, 2008 a ft² numberOfProperties
Portfolio Loan Facility
Real Estate Properties [Line Items]
Extinguishment of debt, amount		$ 136.1
Corporate Centre Technology Mortgage Loan [Member]
Real Estate Properties [Line Items]
Extinguishment of debt, amount	$ 40.6
Campus Drive Buildings | Disposed of by Sale
Real Estate Properties [Line Items]
Consideration		311.0
Closing cost		4.3
Campus Drive Buildings | Disposed of by Sale | KBS Capital Advisors LLC
Real Estate Properties [Line Items]
Disposition fees payable		$ 3.1
100 & 200 Campus Drive [Member] | Office Properties
Real Estate Properties [Line Items]
Number of real estate buildings acquired | numberOfProperties				2
Net rentable area | ft²				590,458
Area of land | a				71.1
300-600 Campus Drive Buildings | Office Properties
Real Estate Properties [Line Items]
Number of real estate buildings acquired | numberOfProperties			4
Net rentable area | ft²			578,388
Area of land | a			64.80