BENEFIT PLANS, Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Prior service costs [Abstract]
Maximum percentage of net gain or loss over the greater of the projected benefit obligation or the market-related value of assets without requiring amortization	10.00%
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 5,081	$ 4,561	$ 4,181
Interest cost	6,264	5,676	5,717
Expected return on plan assets	(14,311)	(14,820)	(13,354)
Plan amendment	0	13	0
Amortization of unrecognized net loss/(gain)	2,568	1,193	767
Amortization of prior service cost	64	(293)	55
Net periodic (benefit)	(334)	(3,670)	(2,634)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	70	69	76
Expected return on plan assets	0	0	0
Plan amendment	0	0	0
Amortization of unrecognized net loss/(gain)	38	21	8
Amortization of prior service cost	(179)	(179)	(179)
Net periodic (benefit)	$ (71)	$ (89)	$ (95)