SEGMENTS - Geographic Concentration (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	100.00%	100.00%	100.00%
Maximum
Geographic concentration
Threshold percentage, unpaid principal balance and related servicing revenues by geographical area	5.00%	5.00%	5.00%
California
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	16.10%	16.20%	16.20%
Florida
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	10.00%	10.40%	9.40%
Texas
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	8.60%	8.80%	9.30%
Georgia
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	5.90%	5.90%	5.80%
All Other States
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	59.40%	58.70%	59.30%