FAIR VALUE MEASUREMENT - Purchase Option Value (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Movement In Purchase Option Value [Roll Forward]
Loss on impairment and write-off of assets	$ (4,400)	$ (4,361)	$ (1,759)	$ (2,521)
Real Estate Loan 1
Movement In Purchase Option Value [Roll Forward]
Purchase option value, beginning balance		1,600
Loss on impairment and write-off of assets		(1,600)
Purchase option value, ending balance	0	0	1,600
Real Estate Loan 2
Movement In Purchase Option Value [Roll Forward]
Purchase option value, beginning balance		2,761
Loss on impairment and write-off of assets		(2,761)
Purchase option value, ending balance	0	0	2,761
Real Estate Loan 3
Movement In Purchase Option Value [Roll Forward]
Purchase option value, beginning balance		2,800
Loss on impairment and write-off of assets		0
Purchase option value, ending balance	$ 2,800	$ 2,800	$ 2,800