PENSION AND OTHER POST-EMPLOYMENT BENEFITS - Schedule of Other Changes to Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	$ 12,794	$ 10,326
Prior service (credit)	0	0
Amortization of:
Prior service credit	0	0
Actuarial (loss) gain	(704)	(492)
Loss recognized related to settlement	(2,162)	0
Total recognized in OCI	9,928	9,834
Expected next fiscal year
Total recognized in OCI	(1,465)
Prior service credit	0
Actuarial (loss) gain	(1,465)
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	(227)	581
Prior service (credit)	(1,400)	(998)
Amortization of:
Prior service credit	1,485	1,120
Actuarial (loss) gain	(3)	248
Loss recognized related to settlement	0	0
Total recognized in OCI	(145)	$ 951
Expected next fiscal year
Total recognized in OCI	801
Prior service credit	730
Actuarial (loss) gain	$ 71