PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Components of cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Components of net periodic benefit cost
Pension settlement expense			$ 1,634	$ 1,085
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	$ 168	$ 1,108	486	2,123
Expected return on plan assets	1	(378)	(89)	(779)
Pension settlement expense	278	431	1,634	1,085
Amortization of net actuarial loss	61	592	210	1,370
Net periodic benefit cost	508	1,753	2,241	3,799
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	10	27	20	54
Amortization of net actuarial loss	23	20	47	40
Net periodic benefit cost	33	47	67	94
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	80	91	160	183
Interest cost	303	210	606	419
Amortization of prior service credit	(8)	(24)	(17)	(47)
Amortization of net actuarial loss	224	76	449	152
Net periodic benefit cost	$ 599	$ 353	$ 1,198	$ 707