GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS - Schedule of Activity Related to Guaranty Obligation (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS
Guaranty obligation, net of accumulated amortization - beginning balance	$ 41,424	$ 35,311	$ 41,187	$ 32,292
Additions, following the sale of loan	3,287	3,046	5,070	7,736
Amortization	(1,950)	(1,885)	(3,757)	(3,466)
Other	(291)	20	(30)	(70)
Guaranty obligation, net of accumulated amortization - ending balance	$ 42,470	$ 36,492	$ 42,470	$ 36,492