GOODWILL AND OTHER INTANGIBLE ASSETS (Net Carrying Amount of Goodwill By Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Beginning balance	$ 85,768	$ 85,768	$ 84,171
Purchase of insurance agency	0	0	1,597
Ending balance	85,768	85,768	85,768
Community Banking
Goodwill [Line Items]
Beginning balance	69,991	69,991	69,991
Purchase of insurance agency	0	0	0
Ending balance	69,991	69,991	69,991
Insurance
Goodwill [Line Items]
Beginning balance	6,788	6,788	5,191
Purchase of insurance agency	0	0	1,597
Ending balance	6,788	6,788	6,788
Investment Management
Goodwill [Line Items]
Beginning balance	8,989	8,989	8,989
Purchase of insurance agency	0	0	0
Ending balance	$ 8,989	$ 8,989	$ 8,989