BENEFIT PLANS, Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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	$ 3,324	$ 3,530	$ 3,988
Interest cost	5,506	5,271	4,120
Expected return on plan assets	(12,169)	(11,922)	(10,149)
Amortization of unrecognized net loss/(gain)	1,466	(307)	4,028
Amortization of prior service cost	8	5	75
Net periodic (benefit) cost	(1,865)	(3,423)	2,062
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	87	102	88
Expected return on plan assets	0	0	0
Amortization of unrecognized net loss/(gain)	(13)	(7)	12
Amortization of prior service cost	(179)	(179)	(179)
Net periodic (benefit) cost	$ (105)	$ (84)	$ (79)