PENSION AND OTHER POST-EMPLOYMENT BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Change in Assumptions for Defined Benefit Plans
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Reduction to pension liability	$ (6,400)		$ (6,400)
Pension Benefits
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Interest cost	2,612	$ 2,390	7,620	$ 7,170
Expected return on plan assets	(3,997)	(4,615)	(13,209)	(13,845)
Amortization of prior service credit	0	0	0	0
Recognized actuarial loss (gain)	73	154	805	462
Pension settlement charge	628	0	5,236	0
Net periodic benefit cost (income)	(684)	(2,071)	452	(6,213)
Other Benefits
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Interest cost	30	43	90	129
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	(182)	(371)	(546)	(1,113)
Recognized actuarial loss (gain)	(18)	1	(54)	3
Pension settlement charge	0	0	0	0
Net periodic benefit cost (income)	(170)	$ (327)	(510)	$ (981)
Qualified Plan
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Voluntary contribution to U.S. pension plan for Union Employees	$ 7,900		$ 7,900