REAL ESTATE HELD FOR INVESTMENT (Operating Leases) (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) tenant	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Operating Leased Assets [Line Items]
Deferred rent recognized	$ (873)	$ 871
Deferred rent receivables	58,000		$ 58,900
Unamortized lease incentives	$ 9,000		9,500
Number of tenants | tenant	185
Recorded bad debt expense related to tenant	$ 71	$ 160
Bad debt reserve	200
Other liabilities, at fair value
Operating Leased Assets [Line Items]
Security deposit liability	$ 2,400		$ 2,600
Maximum
Operating Leased Assets [Line Items]
Operating lease, term	13 years 7 months 6 days
Bad debt reserve of annualized base rent	1.00%
Weighted Average
Operating Leased Assets [Line Items]
Operating lease, term	5 years