GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS - Schedule of Activity Related to Guaranty Obligation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS
Guaranty obligation, net of accumulated amortization - beginning balance	$ 32,292	$ 27,570
Additions, following the sale of loan	16,039	10,597
Amortization	(7,025)	(5,946)
Other	(119)	71
Guaranty obligation, net of accumulated amortization - ending balance	$ 41,187	$ 32,292