UNCONSOLIDATED INVESTMENTS - Contributions to Joint Ventures (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) investment property
Schedule of Equity Method Investments [Line Items]
Non-cash contribution to acquire interest in joint venture | $	$ 125.5
Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Payments to joint venture | $	266.0
Non-cash contribution to acquire interest in joint venture | $	$ 218.0
Western United States [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of properties acquired | property	4
Number of note investments acquired | investment	3
Western United States [Member] | Office Building [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of properties acquired | property	3
United Kingdom [Member] | Office Building [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of properties acquired | property	1