REAL ESTATE AND RELATED LEASE INTANGIBLES, NET - Additional Information (Details) - USD ($) $ in Thousands				3 Months Ended			9 Months Ended
	May 01, 2019	Feb. 06, 2019	Jan. 10, 2019	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Feb. 28, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Foreclosed properties held in real estate				$ 23,900			$ 23,900			$ 6,300
Proceeds from lease prepayments			$ 10,000
Mortgage loan and financing related to property sales		$ 6,600
Gain (loss) on extinguishment/defeasance of debt		$ (1,100)		0		$ (4,323)	(1,070)	$ (4,392)
Impairment of real estate				0	$ 1,400	0	1,350	0
Operating lease income	$ 3,900			24,405			81,106
Loss on sale of real estate	3,500
Depreciation and amortization	400			9,030		10,417	29,192	$ 31,896
Loss on sale of real estate	$ 20
Unbilled rent receivables				1,000			1,000			800
Unencumbered real estates				90,800			90,800			58,600
Real estate operating income				1,100			2,100
Real estate acquired through foreclosure				18,200			18,200
Unamortized discounts included in mortgage loan receivables held for investment, at amortized cost				(100)			$ (100)			$ (500)
Weighted average amortization period for intangible assets acquired							38 years 3 months 18 days	18 years 6 months
Revenues from acquisitions				167		2,000	$ 246	$ 3,400
Net earnings (loss)				(1,000)		$ 700	(2,500)	$ 1,500
Omaha, NE
Business Acquisition [Line Items]
Real estate acquired through foreclosure				18,200			18,200		$ 18,200
Real Estate Acquired in Satisfaction of Debt
Business Acquisition [Line Items]
Loans in default, no losses expected				17,800			17,800
Accrued interest							200
Unamortized discounts included in mortgage loan receivables held for investment, at amortized cost				$ 100			$ 100
Assets Leased to Others
Business Acquisition [Line Items]
Property book value					5,600
Accumulated depreciation and amortization					$ 2,700