RETIREMENT AND POSTRETIREMENT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Retirement and Postretirement Plans [Abstract]
Curtailment loss	$ 1,543
Distributions to Retired Participants [Abstract]
Defined contribution plan description	100% of each employee’s contributions up to 1% of each employee’s compensation plus 50% of each employee’s contributions over 1% but not in excess of 6% of each employee’s compensation for a maximum contribution of 3.5% of a participating employee’s compensation.
Minimum employee contribution percentage	1.00%
Percentage of employer matching contribution	50.00%
Threshold limit percentage of employee compensation	6.00%
Maximum percentage of annual contribution per employee	3.50%
Cash	$ 9,200
Market value of Common Stock from Employee Stock Ownership Plan of BMP (000 shares)	$ 2,400
Returned to treasury Stock	41,101
Gross lump-sum distribution	$ 11,600
Non-cash tax benefit	$ 301
Distribution of common stock (in shares)	88,081
BMP Retirement Plan [Member]
Retirement and Postretirement Plans [Abstract]
Planned contributions/benefit payments	$ 0
Retirement Plans [Member] | BMP, Employee and Outside Director Retirement Plans [Member]
Net Periodic Benefit Cost [Abstract]
Service cost	148
Interest cost	249	$ 183
Expected return on assets	(984)	(428)
Amortization of unrealized loss	206	229
Net periodic benefit credit	(381)	$ (16)
Retirement and Postretirement Plans [Abstract]
Planned contributions/benefit payments	2,800
Actual contributions/benefit payments	6,200
Curtailment loss	$ 1,500