SEGMENTS - Geographic Concentration (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	100.00%	100.00%	100.00%
California
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	17.20%	16.10%	14.90%
Texas
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	8.50%	7.90%	7.50%
Florida
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	8.20%	8.40%	8.50%
Wisconsin
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	5.00%	4.90%	4.10%
Virginia
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	4.00%	4.70%	5.20%
Maryland
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	3.30%	3.60%	6.10%
All other states
Geographic concentration
Percentage of unpaid principal balance of the loans serviced for others	53.80%	54.40%	53.70%
Maximum
Geographic concentration
Threshold percentage, unpaid principal balance and related servicing revenues by geographical area	5.00%