BENEFIT PLANS, Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	$ 4,561	$ 4,181	$ 4,106
Interest cost	5,676	5,717	5,624
Expected return on plan assets	(14,820)	(13,354)	(11,842)
Plan amendment	13	0	20
Amortization of unrecognized net loss/(gain)	1,193	767	1,508
Amortization of prior service cost	(293)	55	43
Net periodic (benefit)	(3,670)	(2,634)	(541)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	69	76	82
Expected return on plan assets	0	0	0
Plan amendment	0	0	0
Amortization of unrecognized net loss/(gain)	21	8	(5)
Amortization of prior service cost	(179)	(179)	(179)
Net periodic (benefit)	$ (89)	$ (95)	$ (102)