SEGMENTS - Geographic Concentration (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	16.20%	16.30%	18.40%
Florida
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	9.40%	9.00%	9.40%
Texas
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	9.30%	9.70%	9.20%
Georgia
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	5.80%	6.10%	4.90%
All other states
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	59.30%	58.90%	58.10%