BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Loans Receivable (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2015	Mar. 11, 2014
Loans receivable
Net impairment (recovery)	$ 0	$ 12
Commercial mortgage loans
Loans receivable
Unamortized acquisition discounts related to sold loans			$ 15,951
PMC Commercial
Loans receivable
Discount on acquisition				$ 33,907
Acquisition discount	$ 1,206