BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Loans Receivable (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2015
Loans receivable
Net impairment (recovery)	$ 0	$ 0	$ 0	$ 12,000
Commercial mortgage loans receivable
Loans receivable
Unamortized acquisition discounts related to sold loans					$ 15,951,000
PMC Commercial
Loans receivable
Discount on acquisition	33,907,000		33,907,000
Acquisition discount	$ 1,068,000		$ 1,068,000