PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Components of cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Components of net periodic benefit cost
Pension settlement expense			$ 8,135	$ 1,603
Noncash charge to pension settlement expense	$ 4,000		4,000
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	138	$ 1,136	624	3,259
Expected return on plan assets	29	(363)	(60)	(1,142)
Pension settlement expense	2,530	518	4,164	1,603
Amortization of net actuarial loss	50	494	260	1,864
Net periodic benefit cost	2,747	1,785	4,988	5,584
Noncash charge to pension settlement expense	4,000		4,000
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	9	27	29	81
Amortization of net actuarial loss	24	20	71	60
Net periodic benefit cost	33	47	100	141
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	80	92	240	275
Interest cost	303	209	909	628
Amortization of prior service credit	(8)	(23)	(25)	(70)
Amortization of net actuarial loss	225	76	674	228
Net periodic benefit cost	$ 600	$ 354	$ 1,798	$ 1,061