SHAREHOLDERS' DEFICIT AND ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Defined benefit plans adjustment | Pension
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Prior service costs	$ (116)	$ 4
Actuarial losses	235	235
Amortization of defined benefit pension and postretirement medical benefits	119	239
Defined benefit plans adjustment | Postretirement Medical Benefits
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Prior service costs	(159)	(318)
Actuarial losses	1,128	2,256
Amortization of defined benefit pension and postretirement medical benefits	969	1,938
Other (loss) income | Unrealized Gains and Losses on Available-for-sale Securities, Net
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Realized losses and (gains) on available-for-sale debt securities	$ 351	$ (911)