PENSION AND OTHER POST-EMPLOYMENT BENEFITS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Change in Assumptions for Defined Benefit Plans
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Reduction to pension liability	$ 5,800		$ 5,800
Pension Benefits
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Interest cost	2,504	$ 2,390	5,008	$ 4,780
Expected return on plan assets	(4,606)	(4,615)	(9,212)	(9,230)
Amortization of prior service credit	0	0	0	0
Recognized actuarial loss (gain)	366	154	732	308
Pension settlement charge	4,608	0	4,608	0
Net periodic pension cost	2,872	(2,071)	1,136	(4,142)
Other Benefits
PENSIONS AND OTHER POSTRETIREMENT BENEFITS
Interest cost	30	43	60	86
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	(182)	(371)	(364)	(742)
Recognized actuarial loss (gain)	(18)	1	(36)	2
Pension settlement charge	0	0	0	0
Net periodic pension cost	$ (170)	$ (327)	$ (340)	$ (654)