PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Components of cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Components of net periodic benefit cost
Pension settlement expense			$ 3,644	$ 2,267
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	$ 1,073	$ 1,057	3,462	3,520
Expected return on plan assets	(763)	(2,242)	(4,984)	(6,346)
Pension settlement expense	943	803	3,644	2,267
Amortization of net actuarial loss	703	1,106	2,346	3,123
Net periodic benefit cost	1,956	724	4,468	2,564
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	26	32	77	97
Amortization of net actuarial loss	20	38	61	114
Net periodic benefit cost	46	70	138	211
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	122	107	366	321
Interest cost	265	254	795	763
Amortization of prior service credit	(47)	(47)	(142)	(142)
Amortization of net actuarial loss	173	177	520	529
Net periodic benefit cost	$ 513	$ 491	$ 1,539	$ 1,471