GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS - Summary of Allowance for Risk-Sharing Obligations (Detail) $ in Thousands	3 Months Ended		12 Months Ended	24 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) loan	Dec. 31, 2013	Mar. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
Allowance for Risk-Sharing Contracts
Beginning balance	$ 11,471	$ 4,622	$ 4,622
Adjustment related to adoption of ASU 2016-13	31,570
Provision for risk-sharing obligations	22,537	2,052
Other	(1,468)	8
Ending balance	$ 64,110	6,682	$ 11,471
Number of defaulted loans | loan			2
Amount of specific reserves placed on defaulted at risk loans							$ 6,900
Number of defaulted at risk loans on which loss sharing settlements were reached | loan			2
Average loss rate for forecasted period	0.01%
Charge off rate in forecasted period	0.07%			0.12%
Weighted average charge off rate for the remaining period					0.0176%	0.0176%
Allowance for risk-sharing obligations	$ 11,471	$ 6,682	$ 4,622		$ 64,110		11,471
Fannie Mae DUS program
Allowance for Risk-Sharing Contracts
Maximum quantifiable contingent liability associated with guarantees					7,700,000
Loans serviced
Allowance for Risk-Sharing Contracts
At risk servicing portfolio					94,800,000		$ 93,200,000
Fannie Mae DUS Program
Allowance for Risk-Sharing Contracts
At risk servicing portfolio					37,200,000
CECL reserve for at risk servicing portfolio					$ 57,200	$ 34,700
Weighted average remaining life of the at risk servicing portfolio	7 years 6 months