EMPLOYEE BENEFIT PLANS (Components of cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of net periodic benefit cost
Pension settlement expense	$ 3,229	$ 3,202	$ 6,595
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost	4,572	5,200	6,039
Expected return on plan assets	(8,607)	(9,180)	(10,419)
Pension settlement expense	3,023	3,202	5,880
Amortization of net actuarial loss	4,087	3,218	2,398
Net periodic benefit cost	3,075	2,440	3,898
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	130	123	184
Pension settlement expense	206		715
Amortization of net actuarial loss	152	159	214
Net periodic benefit cost	488	282	1,113
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	429	406	280
Interest cost	1,017	913	788
Amortization of prior service credit	(190)	(190)	(190)
Amortization of net actuarial loss	705	853	93
Net periodic benefit cost	$ 1,961	$ 1,982	$ 971