SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Provision (Benefit) for Credit Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provision (Benefit) for Credit Losses
Provision (benefit) for loan losses	$ (294)	$ (467)	$ (36)
Provision for risk-sharing obligations	51	(145)	1,680
Provision (benefit) for credit losses	$ (243)	$ (612)	$ 1,644