PENSION AND OTHER POST-EMPLOYMENT BENEFITS - Balance Sheet Components (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent assets	$ 4,245	$ 0
Pension Benefits
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent assets	4,245	0
Current liabilities	0	0
Noncurrent liabilities	(13,930)	(21,671)
Net amount recognized	(9,685)	(21,671)
Amounts recognized in accumulated other comprehensive income (loss) before taxes:
Net actuarial loss	55,923	60,256
Prior service (credit)	0	0
Net amount recognized	55,923	60,256
Other Benefits
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent assets	0	0
Current liabilities	(301)	(231)
Noncurrent liabilities	(3,301)	(3,575)
Net amount recognized	(3,602)	(3,806)
Amounts recognized in accumulated other comprehensive income (loss) before taxes:
Net actuarial loss	1,043	1,015
Prior service (credit)	(2,580)	(3,310)
Net amount recognized	$ (1,537)	$ (2,295)