MORTGAGE BANKING - Economic Assumptions Used to Estimate Value of MSRs Capitalized (Details) - Residential mortgages	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Servicing Assets at Fair Value [Line Items]
Weighted average life (in years)	6 years 1 month 6 days	5 years 10 months 24 days	5 years 9 months 18 days
Weighted average constant prepayment rate	11.00%	10.70%	11.70%
Weighted average discount rate	9.70%	9.70%	10.30%