PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Funded status) (Details) - Nonunion Defined Benefit Pension Plan - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
Change in benefit obligations
Benefit obligations at beginning of period				$ 137,417
Interest cost		$ 1,136	$ 1,073	3,259	$ 3,462
Actuarial loss				3,562
Benefits paid				(11,781)
Benefit obligations at end of period	$ 132,457	132,457		132,457
Change in plan assets
Fair value of plan assets at beginning of period				124,831
Actual return on plan assets				2,028
Employer contributions	5,500			5,500
Benefits paid				(11,781)
Fair value of plan assets at end of period	120,578	120,578		120,578
Funded status at period end	(11,879)	(11,879)		(11,879)
Accumulated benefit obligation	132,457	$ 132,457		132,457
Employer contributions	$ 5,500			$ 5,500
Adjusted funding target attainment percentage						108.77%