REAL ESTATE AND RELATED LEASE INTANGIBLES, NET - Real Estate Properties Sold (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019 USD ($) property	Sep. 30, 2018 USD ($) property	Sep. 30, 2019 USD ($) property	Sep. 30, 2018 USD ($) property	Dec. 31, 2018 USD ($)
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				$ 10,794	$ 153,398
Net Book Value	[1]	$ 981,333		981,333		$ 998,022
Realized Gain/(Loss)		2,082	$ 63,704	963	96,341
2019 Disposal Properties
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				22,913
Net Book Value		21,769		21,769
Realized Gain/(Loss)				1,144
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				$ 4,195
Net Book Value		$ 3,796		3,796
Realized Gain/(Loss)				$ 399
Properties | property		0		0
Units Sold | property				14
Units Remaining | property				8
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
2019 Disposal Properties | Diversified | Grand Rapids, MI
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds				$ 6,970
Net Book Value		$ 4,920		4,920
Realized Gain/(Loss)				$ 2,050
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					213,120
Net Book Value			118,710		118,710
Realized Gain/(Loss)					94,410
2018 Disposal Properties | Condominium | Las Vegas, NV
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					6,228
Net Book Value			$ 3,116		3,116
Realized Gain/(Loss)					$ 3,112
Properties | property			0		0
Units Sold | property					8
Units Remaining | property					5
2018 Disposal Properties | Condominium | Miami, FL
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					$ 4,844
Net Book Value			$ 3,987		3,987
Realized Gain/(Loss)					$ 857
Properties | property			0		0
Units Sold | property					18
Units Remaining | property					30
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
2018 Disposal Properties | Diversified | St. Paul, MN
Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales Proceeds					109,275
Net Book Value			$ 47,627		47,627
Realized Gain/(Loss)					$ 61,648
Properties | property			4		4
Units Sold | property					0
Units Remaining | property					0
2018 Disposal Properties | Diversified | St. Paul, MN | Third Party Investor
Disposal Groups, Including Discontinued Operations [Line Items]
Realized Gain/(Loss)					$ 7,900

[1] Includes amounts relating to consolidated variable interest entities. See Note 10.