FAIR VALUE MEASUREMENT - Schedule of Financial Instruments Measured at Fair Value (Details) - Recurring basis - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
Purchase Options related to real estate loans	$ 8,920	$ 6,120
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	8,920	6,120
Interest rate swaps
Assets:
Derivative asset		3,461
Liabilities:
Derivative liabilities	20,553	5,042
Interest rate swaps | Level 1
Assets:
Derivative asset		0
Liabilities:
Derivative liabilities	0	0
Interest rate swaps | Level 2
Assets:
Derivative asset		3,461
Liabilities:
Derivative liabilities	20,553	5,042
Interest rate swaps | Level 3
Assets:
Derivative asset		0
Liabilities:
Derivative liabilities	$ 0	$ 0