FAIR VALUE MEASUREMENT FAIR VALUE MEASUREMENT - Purchase Option Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Purchase Option Roll Forward [Roll Forward]
Loss on impairment of assets	$ 0	$ 0	$ (782)	$ (1,685)
Real Estate Loan 1
Purchase Option Roll Forward [Roll Forward]
Purchase Option Value, beginning balance			2,382
Loss on impairment of assets			(782)
Purchase Option Value, ending balance	1,600		1,600
Real Estate Loan 2
Purchase Option Roll Forward [Roll Forward]
Purchase Option Value, beginning balance			2,761
Loss on impairment of assets			0
Purchase Option Value, ending balance	2,761		2,761
Real Estate Loan 3
Purchase Option Roll Forward [Roll Forward]
Purchase Option Value, beginning balance			977
Loss on impairment of assets			0
Purchase Option Value, ending balance	977		977
Real Estate Loan 4
Purchase Option Roll Forward [Roll Forward]
Purchase Option Value, beginning balance			2,800
Loss on impairment of assets			0
Purchase Option Value, ending balance	$ 2,800		$ 2,800