PREMISES AND EQUIPMENT - Schedule of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 184,636	$ 180,575
Accumulated depreciation	(66,898)	(59,358)
Premises and equipment, net	117,738	121,217
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	39,299	38,521
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	95,771	94,533
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	48,809	45,988
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 757	$ 1,533