PREMISES AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 241,575	$ 219,775
Accumulated depreciation	(118,182)	(107,457)
Premises and equipment, net	123,393	112,318
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	23,869	22,585
Bank Premises [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	131,647	116,663
Equipment and Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 86,059	$ 80,527