GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS - Schedule of Activity Related to Guaranty Obligation (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS
Guaranty obligation, net of accumulated amortization - beginning balance	$ 51,414	$ 42,470	$ 46,870	$ 41,187
Additions, following the sale of loan	3,729	4,078	13,323	9,147
Amortization	(2,365)	(2,057)	(7,061)	(5,814)
Other	(122)	(78)	(476)	(107)
Guaranty obligation, net of accumulated amortization - ending balance	$ 52,656	$ 44,413	$ 52,656	$ 44,413