LEASES - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Components of lease expense:
Operating lease cost (resulting from lease payments)	$ 3,134	$ 3,397	$ 6,286	$ 6,127
ROU assets obtained in the exchange for lease liabilities due to new leases and acquisitions	$ 0	0	$ 803	0
Weighted average remaining lease term of operating leases	9 years 2 months 12 days		9 years 2 months 12 days		9 years 6 months
Weighted average discount rate of operating leases	2.93%		2.93%		3.04%
Supplemental cash flow information related to leases:
Operating cash flows from operating leases	$ 3,274	3,309	$ 6,554	6,002
Operating lease ROU assets	62,225		62,225		$ 65,215
Lease liability	71,850		71,850		$ 74,982
Revere Bank And RPJ
Components of lease expense:
ROU assets obtained in the exchange for lease liabilities due to new leases and acquisitions	$ 0	$ 7,409	$ 0	$ 7,720