GOODWILL AND OTHER INTANGIBLE ASSETS (Net Carrying Amount of Goodwill By Segment) (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 370,223
No Activity	0
Ending balance	370,223
Community Banking
Goodwill [Roll Forward]
Beginning balance	331,688
No Activity	0
Ending balance	331,688
Insurance
Goodwill [Roll Forward]
Beginning balance	6,788
No Activity	0
Ending balance	6,788
Investment Management
Goodwill [Roll Forward]
Beginning balance	31,747
No Activity	0
Ending balance	$ 31,747