PREMISES AND EQUIPMENT - Summary of premises and equipment, less accumulated depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 74,982	$ 69,673
Less accumulated depreciation and amortization	26,809	22,522
Premises and equipment, net	48,173	47,151
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	6,220	5,987
Land improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	3,842	3,591
Building and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	42,238	39,661
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	4,092	4,092
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 18,590	$ 16,342