DEBT OBLIGATIONS - Secured Credit Facilities (Details)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Nov. 30, 2021 USD ($) debt_instrument	Sep. 30, 2020 USD ($)	Aug. 31, 2017 USD ($)	Oct. 31, 2014 USD ($)
Debt Instrument [Line Items]
Servicing rights, at fair value	$ 2,213,700,000	$ 2,006,712,000
Debt obligations, net	2,427,140,000	1,628,208,000
Trading securities, at fair value	$ 105,308,000	72,874,000
Minimum
Debt Instrument [Line Items]
Advance rate	60.00%
Maximum
Debt Instrument [Line Items]
Advance rate	90.00%
Finance Servicing Rights
Debt Instrument [Line Items]
Debt obligations, net	$ 114,700,000
Pledged as Collateral
Debt Instrument [Line Items]
Servicing rights, at fair value	484,393,000	400,678,000
Pledged as Collateral | Variable Interest Entity, Not Primary Beneficiary
Debt Instrument [Line Items]
Trading securities, at fair value	105,308,000	72,874,000
Secured credit facilities
Debt Instrument [Line Items]
Debt obligations, net	1,436,684,000	542,892,000
Secured credit facilities | 2020-VF1 Notes | Advance Receivables Trust
Debt Instrument [Line Items]
Face amount				$ 130,000,000
Secured credit facilities | 2020-VF1 Notes | Reimbursement For Advances Made
Debt Instrument [Line Items]
Outstanding balance	18,900,000
Secured credit facilities | GMSR VFN | GNMA Mortgage Servicing Rights
Debt Instrument [Line Items]
Face amount	65,000,000
Secured credit facilities | GMSR VFN | Servicing Advance Reimbursement Amounts
Debt Instrument [Line Items]
Outstanding balance	14,300,000
Deferred financing costs	500,000
Number of debt instruments | debt_instrument			2
Secured credit facilities | GMSR VFN | Maximum
Debt Instrument [Line Items]
Face amount					$ 150,000,000
Secured credit facilities | GMSR VFN | Maximum | Servicing Advance Reimbursement Amounts
Debt Instrument [Line Items]
Face amount			$ 150,000,000
Secured credit facilities | Revolving credit facility
Debt Instrument [Line Items]
Borrowing capacity						$ 25,000,000
Outstanding balance	268,000,000
Available borrowing capacity	268,000,000
Debt obligations, net	1,237,269,000	343,759,000
Secured credit facilities | Revolving credit facility | Pledged as Collateral
Debt Instrument [Line Items]
Servicing rights, at fair value	365,700,000
Secured credit facilities | Third Secured Credit Facility
Debt Instrument [Line Items]
Borrowing capacity	300,000,000
Servicing rights, at fair value	600,900,000
Outstanding balance	300,000,000
Line of credit facility, option to increase In borrowing capacity	500,000,000
Deferred financing costs	400,000
Secured credit facilities | Fourth Secured Credit Facility
Debt Instrument [Line Items]
Borrowing capacity	500,000,000
Servicing rights, at fair value	711,200,000
Outstanding balance	425,000,000
Deferred financing costs	1,700,000
Secured credit facilities | Securities financing facilities
Debt Instrument [Line Items]
Debt obligations, net	$ 98,900,000	$ 66,439,000