EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 1,622	$ 1,887	$ 4,866	$ 5,661
Interest cost	4,946	4,546	14,840	13,638
Expected return on assets	(5,077)	(5,213)	(15,231)	(15,639)
Amortization of unrecognized prior service cost	0	23	0	69
Amortization of net loss	2,737	3,987	8,210	11,961
Net periodic benefit cost	4,228	5,230	12,685	15,690
Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	149	186	447	558
Interest cost	601	587	1,803	1,760
Expected return on assets	(531)	(564)	(1,593)	(1,692)
Amortization of unrecognized prior service cost	(416)	(415)	(1,246)	(1,245)
Amortization of net loss	262	435	784	1,307
Net periodic benefit cost	$ 65	$ 229	$ 195	$ 688