PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Components of cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Components of net periodic benefit cost
Pension settlement expense			$ 89	$ 1,634
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost		$ 168		486
Expected return on plan assets		1		(89)
Pension settlement expense		278		1,634
Amortization of net actuarial (gain) loss		61		210
Net periodic benefit cost		508		2,241
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	$ 2	10	5	20
Pension settlement expense			89
Amortization of net actuarial (gain) loss	1	23	5	47
Net periodic benefit cost	3	33	99	67
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	47	80	94	160
Interest cost	144	303	288	606
Amortization of prior service credit		(8)		(17)
Amortization of net actuarial (gain) loss	(149)	224	(298)	449
Net periodic benefit cost	$ 42	$ 599	$ 84	$ 1,198