FAIR VALUE MEASUREMENT - Schedule of Financial Instruments Measured at Fair Value (Details) - Recurring basis - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Purchase options related to real estate loans	$ 6,120	$ 6,078
Level 1
Assets:
Purchase options related to real estate loans	0	0
Level 2
Assets:
Purchase options related to real estate loans	0	0
Level 3
Assets:
Purchase options related to real estate loans	6,120	6,078
Interest rate swaps
Assets:
Derivative asset	5,084	1,509
Liabilities:
Derivative liabilities	21	190
Interest rate swaps | Level 1
Assets:
Derivative asset	0	0
Liabilities:
Derivative liabilities	0	0
Interest rate swaps | Level 2
Assets:
Derivative asset	5,084	1,509
Liabilities:
Derivative liabilities	21	190
Interest rate swaps | Level 3
Assets:
Derivative asset	0	0
Liabilities:
Derivative liabilities	$ 0	$ 0