REAL ESTATE AND RELATED LEASE INTANGIBLES, NET - Real Estate Properties Sold (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($) property	Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($) property	Dec. 31, 2018 USD ($)
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				$ 8,521	$ 90,806
Net Book Value	[1]	$ 984,377		984,377		$ 998,022
Realized Gain/(Loss)		(1,124)	$ 1,628	(1,119)	32,637
2019 Disposal Properties
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				15,665
Net Book Value		16,603		16,603
Realized Gain/(Loss)				(938)
2019 Disposal Properties | Condominium | Las Vegas, NV
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				0
Net Book Value		$ 0		0
Realized Gain/(Loss)				$ 0
Properties | property		0		0
Units Sold | property				0
Units Remaining | property				1
2019 Disposal Properties | Condominium | Miami, FL
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				$ 3,917
Net Book Value		$ 3,550		3,550
Realized Gain/(Loss)				$ 367
Properties | property		0		0
Units Sold | property				13
Units Remaining | property				9
2019 Disposal Properties | Diversified | Wayne, NJ
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				$ 1,729
Net Book Value		$ 4,799		4,799
Realized Gain/(Loss)				$ (3,070)
Properties | property		1		1
Units Sold | property				0
Units Remaining | property				0
2019 Disposal Properties | Diversified | Grand Rapids, MI
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				$ 10,019
Net Book Value		$ 8,254		8,254
Realized Gain/(Loss)				$ 1,765
Properties | property		1		1
Units Sold | property				0
Units Remaining | property				0
2018 Disposal Properties
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					100,578
Net Book Value			68,581		68,581
Realized Gain/(Loss)					31,997
2018 Disposal Properties | Condominium | Las Vegas, NV
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					4,509
Net Book Value			$ 1,939		1,939
Realized Gain/(Loss)					$ 2,570
Properties | property			0		0
Units Sold | property					6
Units Remaining | property					7
2018 Disposal Properties | Condominium | Miami, FL
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					$ 3,296
Net Book Value			$ 2,662		2,662
Realized Gain/(Loss)					$ 634
Properties | property			0		0
Units Sold | property					12
Units Remaining | property					36
2018 Disposal Properties | Diversified | El Monte, CA
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					$ 71,807
Net Book Value			$ 52,610		52,610
Realized Gain/(Loss)					$ 19,197
Properties | property			1		1
Units Sold | property					0
Units Remaining | property					0
2018 Disposal Properties | Diversified | El Monte, CA | Third Party Investor
Disposal Groups, Including Discontinued Operations [Line Items]
Realized Gain/(Loss)					$ 7,000
2018 Disposal Properties | Diversified | Richmond, VA
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					20,966
Net Book Value			$ 11,370		11,370
Realized Gain/(Loss)					$ 9,596
Properties | property			1		1
Units Sold | property					0
Units Remaining | property					0
2018 Disposal Properties | Diversified | Richmond, VA | Third Party Investor
Disposal Groups, Including Discontinued Operations [Line Items]
Realized Gain/(Loss)					$ 400

[1] Includes amounts relating to consolidated variable interest entities. See Note 3.