MORTGAGE BANKING - Economic Assumptions Used to Estimate Value of MSRs Capitalized (Details) - Residential mortgages	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Servicing Assets at Fair Value [Line Items]
Weighted average life (in years)	7 years 3 months 4 days	6 years 2 months 12 days	7 years 5 months 1 day	6 years 7 months 6 days
Weighted average constant prepayment rate	7.60%	11.10%	7.50%	9.90%
Weighted average discount rate	9.80%	9.90%	9.80%	9.90%