PREMISES AND EQUIPMENT (Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Operating Leases, Rent Expense, Net	$ 7.9	$ 7.6	$ 7.3
Maximum
Property, Plant and Equipment [Line Items]
Lease Commitment Initial Term	15 years
Minimum
Property, Plant and Equipment [Line Items]
Lease Commitment Initial Term	3 years
Ground Lease | Maximum
Property, Plant and Equipment [Line Items]
Lease Commitment Initial Term	20 years
Premises and Equipment
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 5.3	$ 5.3	$ 4.6