PREMISES AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Premises and Equipment
Gross premises and equipment	$ 145,755	$ 139,398
Accumulated depreciation and amortization	(97,407)	(91,140)
Net premises and equipment	48,348	48,258
Land
Premises and Equipment
Gross premises and equipment	8,309	8,309
Office buildings and improvements
Premises and Equipment
Gross premises and equipment	100,314	96,898
Furniture, fixtures and equipment
Premises and Equipment
Gross premises and equipment	$ 37,132	$ 34,191