BENEFIT PLANS, Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	$ 4,106	$ 3,324	$ 3,530
Interest cost	5,624	5,506	5,271
Expected return on plan assets	(11,842)	(12,169)	(11,922)
Plan amendment	20	0	0
Amortization of unrecognized net loss/(gain)	1,508	1,466	(307)
Amortization of prior service cost/(credit)	43	8	5
Net periodic (benefit)	(541)	(1,865)	(3,423)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	82	87	102
Expected return on plan assets	0	0	0
Plan amendment	0	0	0
Amortization of unrecognized net loss/(gain)	(5)	(13)	(7)
Amortization of prior service cost/(credit)	(179)	(179)	(179)
Net periodic (benefit)	$ (102)	$ (105)	$ (84)