REAL ESTATE AND RELATED LEASE INTANGIBLES, NET - Additional Information (Details) - USD ($)					1 Months Ended			3 Months Ended	12 Months Ended
	Dec. 18, 2019	May 01, 2019	Feb. 06, 2019	Jan. 10, 2019	Jun. 30, 2020	Dec. 31, 2019	Feb. 28, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Foreclosed properties held in real estate						$ 89,500,000			$ 106,800,000	$ 89,500,000
Proceeds from lease prepayments				$ 10,000,000.0
Mortgage loan and financing related to property sales			$ 6,600,000
Gain (loss) on extinguishment/defeasance of debt			$ (1,100,000)						22,250,000	(1,070,000)	$ (4,392,000)
Impairment of real estate								$ 1,400,000	0	1,350,000	0
Operating lease income		$ 3,900,000							100,248,000	106,366,000	106,177,000
Loss on sale of real estate		3,500,000
Depreciation and amortization		400,000							39,079,000	38,511,000	41,959,000
Loss on sale of real estate		$ 20,000
Unbilled rent receivables						900,000			500,000	900,000
Unencumbered real estates						59,200,000			75,900,000	59,200,000
Real estate operating income									$ 5,600,000	$ 2,600,000
Weighted average amortization period for intangible assets acquired									39 years 9 months 18 days	34 years 2 months 12 days
Revenues from acquisitions									$ 400,000	$ 600,000
Net earnings (loss)									(900,000)	(2,300,000)
Provision for (release of) loan loss reserves									18,275,000	2,600,000	13,900,000
Real estate acquired through foreclosure, fair value						84,150,000			29,310,000	84,150,000
Gain resulting from foreclosure of loan									98,000	2,250,000	0
Realized loss on sale of real estate, net					$ 0				32,102,000	1,392,000	$ 95,881,000
2020 Disposal Properties
Business Acquisition [Line Items]
Realized loss on sale of real estate, net									32,102,000
Los Angeles, California | Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Gain resulting from foreclosure of loan									(100,000)
Omaha, NE | Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Gain resulting from foreclosure of loan							$ 0
South Bend, IN | Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Gain resulting from foreclosure of loan									100,000
Winston Salem, North Carolina | Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Gain on sale of foreclosed property									800,000
Fort Worth and Arlington, TX | Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Gain resulting from foreclosure of loan						0
Diversified
Business Acquisition [Line Items]
Real estate acquired through foreclosure, net basis					3,800,000
Diversified | Los Angeles, California
Business Acquisition [Line Items]
Real estate acquired through foreclosure, net basis									21,600,000
Provision for (release of) loan loss reserves									2,000,000.0
Real estate acquired through foreclosure, fair value									21,535,000
Diversified | Omaha, NE
Business Acquisition [Line Items]
Real estate acquired through foreclosure, net basis							17,900,000
Real estate acquired through foreclosure, fair value							$ 18,200,000
Terminal capitalization rate							8.75%
Discount rate							10.25%
Diversified | South Bend, IN
Business Acquisition [Line Items]
Real estate acquired through foreclosure, net basis									4,100,000
Provision for (release of) loan loss reserves									500,000
Real estate acquired through foreclosure, fair value									3,875,000
Diversified | South Bend, IN | 2020 Disposal Properties
Business Acquisition [Line Items]
Realized loss on sale of real estate, net									0
Diversified | Winston Salem, North Carolina
Business Acquisition [Line Items]
Real estate acquired through foreclosure, fair value					$ 3,900,000				3,900,000
Terminal capitalization rate					9.50%
Discount rate					13.50%
Diversified | Winston Salem, North Carolina | 2020 Disposal Properties
Business Acquisition [Line Items]
Realized loss on sale of real estate, net									844,000
Diversified | San Diego, CA
Business Acquisition [Line Items]
Real estate acquired through foreclosure, net basis						40,000,000.0				40,000,000.0
Real estate acquired through foreclosure, fair value						$ 42,300,000				42,300,000
Terminal capitalization rate	5.75%					8.50%
Discount rate						10.50%
Diversified | San Diego, CA | Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Gain resulting from foreclosure of loan						$ 2,300,000
Mortgage loan receivable						33,900,000
Diversified | San Diego, CA | First mortgage loans
Business Acquisition [Line Items]
Mortgage loan receivable						5,700,000
Diversified | Fort Worth and Arlington, TX
Business Acquisition [Line Items]
Real estate acquired through foreclosure, net basis									$ 22,600,000
Terminal capitalization rate	6.00%
Assumed liabilities						$ (900,000)				$ (900,000)
Diversified | Fort Worth, TX
Business Acquisition [Line Items]
Real estate acquired through foreclosure, fair value	$ 12,800,000
Diversified | Arlington, TX
Business Acquisition [Line Items]
Real estate acquired through foreclosure, fair value	$ 10,900,000
Assets Leased to Others
Business Acquisition [Line Items]
Property book value								5,600,000
Accumulated depreciation and amortization								$ 2,700,000