RETIREMENT AND POSTRETIREMENT PLANS - Net periodic cost for the Employee Retirement Plan (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
BMP and Outside Director Retirement Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Curtailment gain	$ (1,500)
Retirement Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		$ 893
Interest cost		609
Expected return on plan assets		(2,883)
Net periodic (credit) cost		(1,381)
Employee Retirement Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		562	$ 732	$ 901
Expected return on plan assets		(1,846)	(1,713)	(1,528)
Amortization of unrealized loss		824	914	913
Net periodic (credit) cost		(460)	(67)	286
RETIREMENT PLANS | BMP and Outside Director Retirement Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		12	234	351
Curtailment gain		1,543
Amortization of unrealized loss			179	59
Net periodic (credit) cost		$ 1,555	413	410
POSTRETIREMENT PLANS
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost			42	56
Curtailment gain			1,651
Amortization of unrealized loss			(9)	(20)
Net periodic (credit) cost			$ 1,684	$ 36