SHAREHOLDERS' DEFICIT AND ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in Accumulated Other Comprehensive Income by component (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (158,699)
Other comprehensive income before reclassifications	(12,856)
Amounts reclassified from accumulated other comprehensive income (loss)	1,266
Balance at end of period	(170,289)
Defined benefit plans adjustment | Pension
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(19,921)
Other comprehensive income before reclassifications	(45)
Amounts reclassified from accumulated other comprehensive income (loss)	239
Balance at end of period	(19,727)
Defined benefit plans adjustment | Postretirement Medical Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(55,123)
Other comprehensive income before reclassifications	0
Amounts reclassified from accumulated other comprehensive income (loss)	1,938
Balance at end of period	(53,185)
Available for sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(624)
Other comprehensive income before reclassifications	635
Amounts reclassified from accumulated other comprehensive income (loss)	(911)
Balance at end of period	(900)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(44,530)
Other comprehensive income before reclassifications	(12,544)
Balance at end of period	(57,074)
Tax effect of other comprehensive income gains
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(38,501)
Other comprehensive income before reclassifications	(902)
Balance at end of period	$ (39,403)