GUARANTY OBLIGATION AND ALLOWANCE FOR RISK-SHARING OBLIGATIONS - Summary of Allowance for Risk-Sharing Obligations (Detail) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2022 USD ($) loan	Dec. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) loan	Dec. 31, 2020
Allowance for Risk-Sharing Contracts
Beginning balance	$ 62,636		$ 75,313	$ 75,313
Provision (benefit) for risk-sharing obligations	(9,392)		(10,733)
Ending balance	$ 53,244	$ 62,636	64,580	$ 62,636
Number of defaulted loans | loan	3			3
Amount of specific reserves placed on defaulted at risk loans	$ 10,800	$ 10,300		$ 10,300
Fannie Mae DUS program
Allowance for Risk-Sharing Contracts
Maximum quantifiable contingent liability associated with guarantees	$ 10,200,000		$ 9,300,000
Fannie Mae DUS Program
Allowance for Risk-Sharing Contracts
Period of time used to determine the historical loss rate	10 years
Charge off rate for forecasted period			0.04%		0.06%
Charge off rate for the remaining period	0.012%	0.018%		0.018%
At risk servicing portfolio	$ 49,700,000
CECL reserve for at risk servicing portfolio	$ 42,500	$ 52,300		$ 52,300
Weighted average remaining life of the at risk servicing portfolio	7 years 4 months 24 days	7 years 6 months