MORTGAGE SERVICING RIGHTS AND MSR FINANCING RECEIVABLES - Summary of the Geographic Distribution of the Underlying Residential Mortgage Loans (Details) - MSRs - Mortgage Loans	Sep. 30, 2023	Dec. 31, 2022
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	17.10%	17.40%
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	6.00%	6.00%
Washington
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	5.80%	5.90%
New Jersey
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	4.30%	4.40%
Virginia
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	3.60%	3.60%
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	3.30%	3.40%
Georgia
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	3.00%	2.90%
Other U.S.
Schedule of MSRs [Line Items]
Percentage of Total Outstanding Unpaid Principal Amount	38.70%	38.20%