MORTGAGE SERVICING RIGHTS AND MSR FINANCING RECEIVABLES - Summary of the Geographic Distribution of the Underlying Residential Mortgage Loans (Details) - MSRs - Mortgage Loans	Jun. 30, 2022	Dec. 31, 2021
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	100.00%	100.00%
California
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	17.70%	18.10%
Florida
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	8.60%	8.60%
Texas
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	6.20%	6.20%
New York
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	6.10%	6.00%
Washington
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	5.80%	5.60%
New Jersey
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	4.50%	4.50%
Virginia
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	3.50%	3.40%
Maryland
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	3.40%	3.40%
Illinois
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	3.40%	3.40%
Georgia
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	2.90%	3.00%
Other U.S.
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	37.90%	37.80%