PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Components of cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Components of net periodic benefit cost
Pension settlement expense			$ 1,603	$ 3,644
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	$ 1,136	$ 1,073	3,259	3,462
Expected return on plan assets	(363)	(763)	(1,142)	(4,984)
Pension settlement expense	518	943	1,603	3,644
Amortization of net actuarial loss	494	703	1,864	2,346
Net periodic benefit cost	1,785	1,956	5,584	4,468
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	27	26	81	77
Amortization of net actuarial loss	20	20	60	61
Net periodic benefit cost	47	46	141	138
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	92	122	275	366
Interest cost	209	265	628	795
Amortization of prior service credit	(23)	(47)	(70)	(142)
Amortization of net actuarial loss	76	173	228	520
Net periodic benefit cost	$ 354	$ 513	$ 1,061	$ 1,539