REAL ESTATE AND RELATED LEASE INTANGIBLES, NET - Schedule of Real Estate Properties Acquired (Details) - USD ($) $ in Thousands	1 Months Ended									8 Months Ended	9 Months Ended
	Sep. 30, 2019	Aug. 31, 2019	Jul. 31, 2019	Jun. 30, 2019	Apr. 30, 2019	Feb. 28, 2019	May 31, 2018	Apr. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Purchase Price										$ 13,904	$ 32,104	$ 115,548
Real estate acquired through foreclosure	$ 18,200									$ 18,200	$ 18,200
Lithia Springs, GA | Diversified
Business Acquisition [Line Items]
Purchase Price									$ 24,466
Ownership Interest												70.60%
Lithia Springs, GA | Diversified | Corporate Joint Venture
Business Acquisition [Line Items]
Purchase Price												$ 2,900
Kirbyville, MO | Net Lease
Business Acquisition [Line Items]
Purchase Price								$ 1,156
Ownership Interest												100.00%
Gladwin, MI | Net Lease
Business Acquisition [Line Items]
Purchase Price								1,171
Ownership Interest												100.00%
Foley, MN | Net Lease
Business Acquisition [Line Items]
Purchase Price								1,176
Ownership Interest												100.00%
Moscow Mills, MO | Net Lease
Business Acquisition [Line Items]
Purchase Price								1,237
Ownership Interest												100.00%
Wonder Lake, IL | Net Lease
Business Acquisition [Line Items]
Purchase Price								$ 1,255
Ownership Interest												100.00%
Isla Vista, CA | Diversified
Business Acquisition [Line Items]
Purchase Price							$ 85,087
Ownership Interest												75.00%
Isla Vista, CA | Diversified | Corporate Joint Venture
Business Acquisition [Line Items]
Purchase Price												$ 4,600
Houghton Lake, MI
Business Acquisition [Line Items]
Purchase Price						$ 1,242
Ownership Interest	100.00%									100.00%	100.00%
Trenton, MO
Business Acquisition [Line Items]
Purchase Price						1,164
Ownership Interest	100.00%									100.00%	100.00%
Centralia, IL
Business Acquisition [Line Items]
Purchase Price					$ 1,242
Ownership Interest	100.00%									100.00%	100.00%
Fayette, MO
Business Acquisition [Line Items]
Purchase Price				$ 1,423
Ownership Interest	100.00%									100.00%	100.00%
Dexter, MO
Business Acquisition [Line Items]
Purchase Price			$ 1,150
Ownership Interest	100.00%									100.00%	100.00%
Caledonia, MI
Business Acquisition [Line Items]
Purchase Price			$ 1,199
Ownership Interest	100.00%									100.00%	100.00%
Poseyville, IN
Business Acquisition [Line Items]
Purchase Price		$ 1,220
Ownership Interest	100.00%									100.00%	100.00%
Chillicothe, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,445
Ownership Interest	100.00%									100.00%	100.00%
Sullivan, IL
Business Acquisition [Line Items]
Purchase Price	$ 1,496
Ownership Interest	100.00%									100.00%	100.00%
Becker, MN
Business Acquisition [Line Items]
Purchase Price	$ 1,185
Ownership Interest	100.00%									100.00%	100.00%
Adrian, MO
Business Acquisition [Line Items]
Purchase Price	$ 1,138
Ownership Interest	100.00%									100.00%	100.00%
Omaha, NE
Business Acquisition [Line Items]
Real estate acquired through foreclosure	$ 18,200					$ 18,200				$ 18,200	$ 18,200
Ownership Interest	100.00%									100.00%	100.00%