SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Guaranty Obligation and Allowance for risk sharing obligations (Details) - Fannie Mae DUS program - Maximum	3 Months Ended
Mar. 31, 2020
Debt
Term of debt	15 years
Maximum delinquency period of loans at which initial loss recognition occurs	60 days
Amount of loss absorbed at time of loan default as a percent of the origination unpaid principal balance	20.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration