BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Loans Receivable (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2015
Loans receivable
Net impairment (recovery)	$ 0	$ 137,000	$ 0	$ 149,000
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	$ 958,000		$ 958,000