GOODWILL AND OTHER INTANGIBLE ASSETS (Net Carrying Amount of Goodwill By Segment) (Detail)	6 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill [Line Items]
Beginning balance	$ 347,149,000
Ending balance	370,547,000
Acquisition of Rembert Pendleton Jackson [Member]
Goodwill [Line Items]
Goodwill aquired during the period	22,559,000
Acquisition of Revere Bank [Member]
Goodwill [Line Items]
Goodwill aquired during the period	839,000
Community Banking
Goodwill [Line Items]
Beginning balance	331,173,000
Ending balance	332,012,000
Community Banking | Acquisition of Rembert Pendleton Jackson [Member]
Goodwill [Line Items]
Goodwill aquired during the period	0
Community Banking | Acquisition of Revere Bank [Member]
Goodwill [Line Items]
Goodwill aquired during the period	839,000
Insurance
Goodwill [Line Items]
Beginning balance	6,788,000
Ending balance	6,788,000
Insurance | Acquisition of Rembert Pendleton Jackson [Member]
Goodwill [Line Items]
Goodwill aquired during the period	0
Insurance | Acquisition of Revere Bank [Member]
Goodwill [Line Items]
Goodwill aquired during the period	0
Investment Management
Goodwill [Line Items]
Beginning balance	9,188,000
Ending balance	31,747,000
Investment Management | Acquisition of Rembert Pendleton Jackson [Member]
Goodwill [Line Items]
Goodwill aquired during the period	22,559,000
Investment Management | Acquisition of Revere Bank [Member]
Goodwill [Line Items]
Goodwill aquired during the period	$ 0