MORTGAGE BANKING - Economic Assumptions Used to Estimate Value of MSRs Capitalized (Details) - Residential mortgages	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Servicing Assets at Fair Value [Line Items]
Weighted average life (in years)	6 years 6 months	5 years 8 months 12 days	6 years 7 months 6 days	5 years 10 months 24 days
Weighted average constant prepayment rate	10.80%	12.30%	10.20%	11.70%
Weighted average discount rate	9.90%	9.80%	9.90%	9.80%